Melissa Peacock told police that, when she found her elderly mother dead in bed, she shut the door and carried on as if nothing had happened.
Her mother, Noreen Peacock, was a "delightful" woman, often seen gardening at her home in Kellyville in Sydney's north-west, where she lived with Melissa, her sole carer.
But, from 2009, Mrs Peacock began showing signs of dementia – she wandered the streets and saw people who were not in the room.
On October 18, 2013, two real-estate agents doing a rental inspection found Mrs Peacock "largely mummified" and covered in blankets in her bed, Glebe Coroner's Court heard on Wednesday.
Mrs Peacock was 83 when she died.
Ian Bourke, SC, counsel assisting the inquest into Mrs Peacock's death, said police then began searching for Melissa, who was found staying in a city hotel a week later.
Melissa told police that she got shingles in July 2013, which incapacitated her, at the same time as her mother fell ill with a vomiting bug, Mr Bourke said.
She told officers she got up for work one day in late July, and found her mother's body.
"She claimed ... she shut the door to her bedroom and told nobody about the death and carried on as though her mother was still alive," Mr Bourke said. "She told police she was in denial."
The inquest heard that Melissa was a valued receptionist, who worked six days a week at a northern Sydney private hospital, while also caring for her mother.
He said Melissa's sisters, Debra Crozier and Jaslyne Haywood, had limited contact with Mrs Peacock and last saw her on Mother's Day 2012.
On that day, there was discussion about whether to put Mrs Peacock in a nursing home but Melissa was "adamant" she would never put their mother into care.
As Mrs Peacock's heath declined, Melissa began drinking a lot of sparkling wine to "obliterate what she had to think about", Mr Bourke said.
Police found 150 empty wine bottles in the house and 200 in the garage.
"Unfortunately despite the pressure Melissa was under ... she did not ask for help.
"It appears on the evidence gathered that the level of care given to Noreen diminished significantly during the first half of 2013."
Inspector Katie Orr, the officer in charge of the investigation, agreed that her police report was very critical of Melissa.
"I would not have expected her to give up her job but I would have expected her to ask for help to care for her mother," Inspector Orr said, under cross-examination from Melissa's barrister Greg James, QC.
Inspector Orr agreed that she was also critical of Mrs Crozier and Mrs Haywood.
The inquest has heard that Melissa faced a fraud charge related to operating a bank account without authority and for failing to report her mother's death.
Both charges were dealt with by a court under the Mental Health Act, and no conviction was recorded.
The inquest continues before Deputy State Coroner Sharon Freund.
