Nancy Margaret White, 50, was found in an emaciated condition, covered in vomit, the day before she died on September 6, 2022.
An inquest opened on Monday into the death of Ms White, who also had impaired mobility and limited verbal communication.
Paramedics found Ms White in an emaciated condition on September 5, weighing about 40kg and suffering hypothermia.
"Her bed linen, pillows and jumper were heavily soiled with vomit," counsel assisting the coroner Laura Crase said in her opening address to the South Australian Coroners Court.
She was taken to hospital and assessed as frail and deconditioned.
Ms Crase said the inquest would examine what could be done to better safeguard people like Ms White, and support those who undertake the challenging task of caring for them.
That would ensure others are not overlooked when left without an advocate willing or able to navigate the National Disability Insurance Agency, she said.
A representative from the agency is expected to give evidence on process changes made since Ms White's death.
That evidence could help Ms Roper assess whether the changes "will reduce the likelihood of another vulnerable person like Nancy slipping through the cracks of the system," she told Ms Roper.
Ms White's brother Norman White had been acting as full-time carer for his sister since their parents died.
The siblings had moved to Adelaide from Tasmania in 2018. Ms White was admitted to Flinders Medical Centre in August 2021 after seizures, and she lost significant weight while in hospital.
A social worker raised concerns about discharging Ms White into her brother's care, but he told hospital staff his sister did not want to go to a care facility and he could continue to care for her at home.
At a multidisciplinary team meeting, it was suggested Ms White may be eligible for support.
She was released into her brother's care on October 1, 2021.
An NDIS plan worth $75,000 a year was approved on November 18.
But it was not touched before she died on September 6 the following year.
NDIS staff made numerous calls to Mr White to action the plan, but he later said that "he never got around to setting it up - that he just took care of everything himself," Ms Crase said.
"He just took care of everything himself, and he was not very good at reading," she said.
"Your Honour may find that completing the NDIS paperwork while simultaneously caring for Nancy was simply too difficult for Norman."
Ms White died of acute peritonitis caused by a perforation to her small bowel.
The inquest continues.
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