She said a Thailand-based doctor told her he'd had success "with many similar patients."
"I feel this is the path I have to take, I will do anything for these little girls."
But Ferreira's aunt, Ann Brandon, said the clinic fed off her niece's desperation. Experts say there is no evidence the treatment offered by the clinic would work on someone with advanced cancer.
Ferreira had received chemotherapy and radiotherapy and she was told her only remaining option was palliative chemotherapy.
Brio Clinic offered treatments like "hyperthermia," "high-intensity focused ultrasound," "pH transformation therapy," immunotherapy, "infusions of micellized nutrients" and "GcMAF" - which creators claim is "the best treatment yet found for tumour cancers and 50 other diseases."
But Cancer Society medical director and oncologist Dr Christopher Jackson told the Herald on Sunday there was no evidence that any of the treatments offered could extend the duration or improve the quality of life of a patient with terminal cancer.
Brandon said Ferreira begged her aunt to take her to Thailand. "Amanda was so desperate. She just begged me. So I did it, because of love. "
At the clinic, Ferreira was given "infusions", special blankets were put on her, she lay on sauna beds and received pulses of light on body parts.
But in late March, Ferreira - whose cancer had moved from the liver to her spine - complained of a toothache.
Several dentists said there was nothing wrong. She took a turn for the worse, and on April 20, she was vomiting, not sleeping, and in constant pain. She was given antibiotics by Brio Clinic staff.
On April 28, a friend flew to Thailand and took her to hospital. Half of Ferreira's face was paralysed and her eye wouldn't close. She was dosed up with steroids and painkillers. On her return to New Zealand her doctors saw the cancer had spread to her base of her skull.
"She came home in the most appalling condition," Brandon said.
"She went to hospice and never came home again."
Brandon said after Ferreira left Brio Clinic, they heard nothing. She felt the clinic should have told her they couldn't help Ferreira. "But no. They kept on with the charade, taking more and more money."
Ferreira's mother Liz James agreed. " They should have sent her home. I believe it's all about money - it's immoral," said James, who is also battling cancer.
Last week the Herald on Sunday revealed 26-year-old Holly Devine, who was battling melanoma, had tried to raise money for a $130,000 experimental treatment at the Brio Clinic that she saw as her last chance of living.
But researcher Dr Shaun Holt said magic bullets and cancer-curing clinics weren't real. "I would advise people not to go to an overseas alternative cancer treatment centre. The chances of success are minuscule and there will almost always be a very high charge associated."
The Ministry of Health's Acting Chief Medical Officer, Dr Andrew Simpson, said careful consideration was given to the range of treatments publicly funded in New Zealand.
He advised consumers to make evidence-based decisions in conjunction with health professionals.
Brio Clinic has not responded to questions from the Herald on Sunday.