The girl had wanted to be 'cryo-preserved' after her death, in the hope she could be 'woken up' if doctors found a cure for her rare form of cancer - and wrote to a High Court judge begging for her wishes to be respected.
She died last month and is now suspended in freezing nitrogen at a cryogenic centre in the US.
Her extraordinary case yesterday sparked a fierce debate over the ethics of cryo-freezing - and about the lack of regulation surrounding the cryonics industry in Britain and worldwide.
The teenager, from London, was diagnosed with a rare form of cancer in August last year and announced her wish to be cryo-preserved after all treatment options failed.
She researched the process online and told relatives in the months before her death: "I'm dying but I'm going to come back in 200 years."
Her case was heard by the High Court after her estranged father opposed the plan, saying he could not fund the £37,000 procedure at a facility in the US.
The girl's maternal grandparents agreed to pay all costs but the father still questioned what kind of future the procedure offered to his daughter.
Speaking yesterday the girl's father told the Mail: "We came to the end of the road after my child passed away, what is there left to say?
"It's all ended, it's finished. Her mother didn't allow me to have contact with her.
"I've ended up in court on ten occasions in an effort to see her.
"I've been trying very hard to have contact with her though courts. I was able to see her in 2005 for about a year and a half."
The father, who is in his 40s, said he had been fighting in the courts for access to see his daughter since 2002, when he is understood to have separated from her mother soon after her birth.
He said he made several attempts through the courts to see her, including asking to visit her in hospital and to be allowed to see her body after her death. But he said he last saw her in 2007, adding: "The reason for this is purely her mother's doing. She said no way, full stop.
"As a result of her hatred she caused all this sadness between me and my daughter and she died in the end without me being able to see her.
"It's so sad. My daughter didn't even know about the court proceedings. I am very sad about it. I'm suffering from cancer myself."
Meanwhile another family member suggested last night that she had been 'brainwashed' by people on the internet who were just after money.
A paternal uncle of JS said that the child's mother would not let the family get a second opinion on the freezing procedure.
He described Cryogenic companies as 'hope-traders', adding: "They are just trying to get money off people. Who is going to come back in 200 years? Please tell me? They trade in hope and brainwash people on the internet.'"
"I talked to doctors and professors and scientists and no one thinks it's possible. None of my family on this side supported this process. We wanted JS to have a grave in the earth so we could visit her and pay our respects."
But even relatives on her mother's side of the family said they too had misgivings about the girl being cryogenically preserved.
A cousin of the girl's mother told the Telegraph: "She wouldn't let any of the family see JS. I know about her body being frozen. It's her choice, she wanted to do it and her mum made it happen.
"JS's father didn't know anything at first - the mother wouldn't tell anyone. It was her mum who was driving it. It's not going to work - this cryo thing must be impossible.
"To me, the mum had a problem. They had a bad divorce. She made life hard for JS's father. You know, he was ill and he ended up in the same hospital as JS. He was on a different floor from her for months and he was never told his daughter was so near.
"And then when he heard about the freezing, JS's mum wouldn't let him anywhere near her."
Earlier, the father Mr S had told the High Court: "Even if the treatment is successful and she is brought back to life in, let's say, 200 years, she may not find any relative and she might not remember things.
"She may be left in a desperate situation - given that she is still only 14-years-old - and will be in the United States of America."
Mr Justice Peter Jackson was called a 'hero' by the child before she died after he agreed to her dying wish so that one day she could 'be cured and woken up'.
The judge also revealed her father was also persuaded in the end and said: 'I respect the decisions she is making. This is the last and only thing she has asked from me.'
During the landmark case she wrote an extraordinary letter to a judge while on her death bed.
She said: "I am only 14-years-old and I don't want to die but I know I am going to die.
"I want to live and live longer and I think that in the future they may find a cure for my cancer and wake me up. I want to have this chance. This is my wish."
"I think being cryo-preserved gives me a chance to be cured and woken up - even in hundreds of years' time. I don't want to be buried underground".
She had asked the High Court to rule that her mother should be the only person allowed to make decisions about the disposal of her body.
After agreeing, High Court judge Mr Justice Jackson, who visited the girl's bedside shortly before her death on October 17, said the terminally ill she died peacefully knowing that her remains would be frozen.
The judge said he had been moved by the 'valiant way' in which she had faced her 'predicament'.
Today the girl's solicitor, Zoe Fleetwood, said the teenager described Mr Justice Jackson as her 'hero' after being informed of the court's decision days before her death.
Ms Fleetwood told the BBC Radio 4 Today programme: "By October 6, the girl knew that her wishes were going to be followed. That gave her great comfort. Very sadly she died on October 17. She had those last few days knowing that her wish was granted."
She added: "It was a great privilege to represent her. She had extraordinary determination.
"When the decision was communicated to her on October 6, she was very pleased. She was delighted and she wanted to see the judge. The judge did go and see her the very next day. She communicated to me after the meeting and she referred to the judge as Mr 'Hero' Peter Jackson."
Her body has been flown to America and she has since slowly been chilled over two to three weeks in Liquid Nitrogen and stored next to around 150 other bodies.
She is in one of America's two main cryo-facilities - the Cryonics Institute near Detroit - where its founder Robert Ettinger was frozen with two of his wives when he died aged 92.
Around 250 people have spent huge sums cryo-preserving their bodies - the first was Dr James Bedford in 1967 - and it has been a popular theme in movies such as Forever Young starring Mel Gibson.
Thousands more have paid up to £150,000 to do the same when they die.
A device called a 'heart-lung resuscitator' is used to get the blood pumping through the body again, when required, and medication is applied to the body to prevent the cells from deteriorating.
Blood and bodily fluids are drained, then they are replaced with a solution like antifreeze.
But the process is hugely controversial, especially with scientists and doctors, because it has never been possible to successfully revive a human or any mammal frozen in this way.
The freezing process was carried out 'quite swiftly' after the teenager's death, said Ms Fleetwood.
She added: "It was a difficult process. Some might say the girl's mother's attention was directed towards that procedure rather than grieving at that time.
"But her daughter had passed away. The procedure needed to be carried out. One can't imagine what this parent was going through at this time from the loss of her daughter. But parents' attention can be directed elsewhere with various arrangements after a person's death."
Ms Fleetwood said the case came to court for the first time on September 26 and was swiftly dealt with in little over a week in "an extraordinary process very sensitively carried out with respect to the family who are grieving at this time".
The case did not create a precedent with regard to the right to be frozen in the hope of future reawakening, said the solicitor.
"The case was not about the rights and wrongs of cryo-preservation," she said. "In accordance with the children's case which go before the courts, this case is about the child's welfare and her wishes being followed."
Some, like the British girl, have their entire bodies frozen, but others only have their heads and brains preserved.
The Alcor Life Extension Foundation in Scottsdale, Arizona and the Michigan-based Cryonics Institute are the world's leading centres.
There is also a large body freezing facility it Russia.
Before she died of a rare and aggressive cancer, the British girl's mother raised£37,000 she needed for the 'freezing of the body in perpetuity', the High Court heard.
But because she is a child it required the consent of both her parents and her father, who had not seen her for eight years, refused.
He had been concerned about consequences of his daughter being cryogenically preserved, and had been concerned about the costs involved.
Mr Justice Jackson said he had made decisions relating to a dispute between parents - not about the rights and wrongs of cryogenic preservation.
But he has suggested that ministers might consider 'proper regulation' of cryonic preservation and revealed that the management of the London hospital she died in had misgivings about her wish.
The girl, who lived in the London area with her mother and had a rare form of cancer diagnosed in August 2015, had to take legal action to be frozen.
After a year of cancer treatment, this was stopped, before she died friends said she was much-loved, 'caring' and 'bubbly' teenager.
It is unclear what kind of post-mortem procedures were performed. Practitioners are known to cover the head with bags of ice to chill the brain. Blood is drained and replaced with antifreeze.
Some patients opt for a cheaper 'head-only' option. The procedure, though deeply controversial, is apparently legal and entirely unregulated.
Mr Justice Jackson admitted: "I have received information about procedures performed on the body after death that would be disturbing to many people."
Remembered by classmates as a 'bubbly' and 'caring' girl who loved to laugh, the teenager - who cannot be named for legal reasons -had written a letter to the court saying how she did not want to be 'buried underground'. She said cryo-preservation gave her the chance to be cured and woken - 'even in hundreds of years' time'.
The girl's body is now suspended in freezing nitrogen at Michigan's Cryonics Institute near Detroit.
Case notes tell how her body, packed in dry ice, arrived at the facility in Flint in October, eight days after her death before being placed in a 'cryostat' - a cold storage chamber. Dry ice has a temperature of -78C(-108F).
Liquid nitrogen is much colder at -196C (-321F). Two further bodies have arrived since. 'Patient 144' was a 56-year-old whose body arrived by private jet, and Patient 145 was a 78-year-old who was frozen within two hours of dying.
Cryonics UK, the not-for-profit group which dispatched the body to the USA, is led by Tim Gibson, a 45-year-old landlord who trains his members how to prepare bodies for freezing. His group is not subject to regulation by the Human Tissue Authority. He once said: "These days, no one blinks an eyelid. Not long ago, they saw us as cranks."
Martin Ingvar, a cognitive neuroscientist at Sweden's Karolinska Institute said the cryogenic process was bound to fail and accused its practitioners of charlatanism.
"When you look at the brain, with 100 billion cells and 10,000 links between these and other cells... there's no way in hell you can restore the function in that," he said.
Cryonics UK said protocols were carried out with the permission of the hospital but some senior staff 'appeared to be on the back foot'.
Tim Gibson, who runs the team, said his volunteers gave the 14-year-old the best chance of success.
Mr Justice Jackson said they had put pressure on hospital staff and were disorganised.
He said: "The little girl who has just been preserved wouldn't have been preserved without us. It was too difficult.
"Without us, the best she could have hoped for would be relying on a funeral director to pack her in dry ice and send her to America."
Members, who can pay up to £28,000 for the standby service, are asked to give the team notice so it can arrive 12 to 24 hours before they are legally pronounced dead.
He signed up to be frozen when he was 20 and said today: "I'm perfectly willing to take the risk with almost a zero possibility chance of success because it's a better chance than being buried."
Mr Gibson, who was trained by the Alcor cryonics preservation service in Arizona, said medical training is not necessary but volunteers need a certain amount of knowledge.
He said: "Initially, I was trained by Alcor in the US, the rest of it just came from practical experience.
"You end up teaching parts of it to newcomers, that really hones your knowledge, you realise what you're missing from your skill-set, you just pick stuff up."
It said in a statement: "This may have been because they had not encountered a cryopreservation before, due to the involvement of the court or because the patient was a minor".
Hospital chiefs failed to respond to requests for comment.
Mr Justice Jackson has asked the Human Tissue Authority to view case files and investigate the issue. A spokesman for the authority said it was now gathering information on any risks posed by cryopreservation and the possible need for regulation.
The frozen 'fountain of youth'? Or false hope for those desperate to live forever? Controversial cryonics method sees people suspended in time waiting for a medical miracle
It is illegal to place a living human into cryonic preservation and the process can only be carried out once a client has been declared dead.
While some chose to preserve their whole body, which can cost up to £150,000, others opt for the cheaper option of freezing just their brain at a cost of £60,000, in the hope it can be transplanted into a living body.
All this is done despite no evidence a human or any other animal can survive the process.
The preservation process begins by moving a body to an ice bed and cover them in a loose, slushy layer of ice.
A device called a 'heart-lung resuscitator' is used to get the blood pumping through the body again, and medication is applied to the body to prevent the cells from deteriorating.
Blood and bodily fluids are drained, then they are replaced with a solution like antifreeze.
Major blood vessels are then flushed of any blood before being swabbed with the antifreeze solution.
The antifreeze solution is used so that ice crystals do not form and damage any cells.
The body is then cooled down to about 0.5 degrees Celsius every hour until the final temperature of -196 degrees C achieved over three weeks then the frozen body is stored.
According to experts, there is no evidence that a whole human body can survive the process.
"Cryopreservation is a remarkable technology which allows us to store living cells, almost indefinitely, at ultra-low temperatures," said Professor Barry Fuller, Professor in Surgical Science and Low Temperature Medicine at UCL.
"It has many useful applications in day to day medicine, such as cryopreserving blood cells, sperm and embryos.
"We have learnt that to survive the process, cells have to be treated with special non-toxic antifreezes, and to be handled in very specific ways. In fact, if they are to survive, frozen cells are not 'frozen' - they must contain no ice crystals, which would otherwise invariably kill them.
"However, cryopreservation has not yet been successfully applied to large structures, such as human kidneys for transplantation, because we have not yet adequately been able to produce suitable equipment to optimise all the steps," Professor Fuller added.
"This is why we have to say that at the moment we have no objective evidence that a whole human body can survive cryopreservation with cells which will function after rearming."
Matheryn Naovaratpong, from Thailand, is thought to be the youngest person ever cryogenically preserved.
The toddler was diagnosed with an aggressive form of cancer last April after she failed to wake up one morning, Motherboard's Brian Merchant reports
After being admitted to a Bangkok hospital, tests revealed she had a 11cm tumour in the left side of her brain.
In 2013 Kim Suozzi, 23, of St Louis, ignored the wishes of her religious family and decided to have her head placed in cryogenic storage after she entered into the final stages of her life.
Diagnosed with an aggressive form of Glioblastoma multiforme, Kim died on January 17th and spent the final two weeks of her life at a hospice in Scottsdale, Arizona, so that she was near to the cryopreservation center that she chose.
Kim had used the website Reddit to successfully help raise the $70,000 in funds she needed to fulfil her desire to have her head placed in cryonic preservation.
