Rosa Maria Maione came before Adelaide Magistrates Court on Wednesday and admitted unlawfully killing Ms Smith.

She will now face the Supreme Court for the start of the sentencing process.

Prosecutors made no application to revoke Maione's bail, but said an application was likely at Maione's arraignment in September.

Police previously alleged Ms Smith died of serious criminal neglect and her death was preventable.

The 54-year-old passed away in hospital in April last year from septic shock, multiple organ failure, severe pressure sores and malnourishment.

She had been found to be living in squalid conditions in her own home, largely confined to a cane chair, while under the care of the National Disability Insurance Scheme.

In the period leading up to her death, Maione had worked as her carer.

Earlier this year a former schoolmate of Ms Smith said her treatment and death remained "incomprehensible".

In a statement read to the Disability Royal Commission the woman relayed a moving account of their longtime friendship.

The pair had gone to primary school together in Adelaide and had kept in touch during high school and as adults but had lost touch in the year before her death because of a falling out.

"This is something I really struggle with. I shouldn't have made excuses," the woman said.

"I carry a lot of guilt about that and I know that things would have been different if I had gone around to see her.

"For me, it is still incomprehensible what has happened to her."

As well as the SA police investigation, the NDIS Quality and Safeguards Commissioner Graeme Head launched an independent inquiry by former Federal Court judge Alan Robertson, with his report last year essentially clearing the commission in how it exercised its regulatory functions.

Mr Robertson said on the question of whether it should have acted earlier to ban Maione, the commission had no information to take such action before Ms Smith's death.

Australian Associated Press