Churchward had done well at school but came under the influence of her cousins and began drinking and smoking cannabis after she and her mother relocated from Auckland to Opotiki when she was 13.
Her behaviour became increasingly antisocial and after her mother apparently rejected her she was placed in the care of an aunt in Auckland.
Churchward again did well at school and talked of going to university, but in the months before the murder she entered into an abusive relationship with a gang member who was just released from prison.
She started using more serious drugs, including methamphetamine, and dabbled in shoplifting.
Ten days before the murder, Churchward was severely beaten by her partner and returned to Opotiki, with her mother saying she looked thin and withdrawn.
Dr Chaplow's report said Churchward was able to succeed in stable environments but was susceptible to peer pressure and had an undeveloped sense of self, in part due to her abandonment by father figures.
Her need to fit in with peers and to keep her promise to her cousin led to her supporting Te Wini in breaking into the house.
The thrill of the robbery for the reward of money to buy cannabis was not maturely balanced with the consequences of harming an innocent person, being caught and being held to account, the report said.
Ms Bellve-Wack also noted Churchward had not developed a stable sense of identity and self-esteem.
Her inability to meet expectations meant she seemed to identify with family members who themselves had serious problems and formed co-dependent relationships with them.
She suffered depression and symptoms of post-traumatic stress disorder, which led her to turn to drugs and alcohol, adding to her problems.
The Crown argued the sentencing judge made no error in imposing the 17-year minimum, saying Churchward's youth alone was not enough to reduce her sentence.
There were aggravating factors in the brutal crime, including its premeditated nature and the vulnerability of the elderly victim.
But Court of Appeal justices Ellen France, Susan Glazebrook and Rhys Harrison said the sentencing judge did not have access to the reports it did.
Had the psychological reports and other factors been taken into account, the sentence would have been significantly less than 17 years.
The court said the sentence was manifestly unjust and could have a "crushing effect" on Churchward, noting 17 years was almost as long as her life up to the time of her conviction.
It dismissed an appeal against conviction, but granted Churchward's lawyers more time to gather further evidence for appeal.
The court in June granted Te Wini a retrial.
