Rosa Maria Maione will face the South Australian Supreme Court on Thursday when Justice Anne Bampton is due to impose both a head sentence and a non-parole period.
Maione is already behind bars after her bail was revoked following final submissions last week.
As part of those submissions, the 69-year-old offered a tearful apology.
"I'm so sorry that my actions have caused so much distress," Maione said in a short statement.
"I pray with all my heart that Annie is in heaven. I ask for Annie's forgiveness, knowing that nothing I say can ever bring her back.
"I will bear this guilt for the rest of my life."
Ms Smith passed away in hospital in April 2020 from septic shock, multiple organ failure, severe pressure sores and malnourishment.
The 54-year-old 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 the death, Maione had worked as her carer.
At an earlier court hearing, Ms Smith's family said there was some relief in Maione's guilty plea.
"She's finally stood up to be counted. But it's too late," the victim's uncle Glenn Smith said.
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