Jessica Camilleri, 27, was found guilty of the manslaughter of her mother Rita in St Clair in July 2019.
Watch a full report of the crime in the video above
She was on Friday sentenced to 21 years and seven months, with a non-parole period of 16 years and two months.
Justice Helen Wilson described the attack as one of the most serious instances of manslaughter, saying the crime of extraordinary viciousness and brutality was made worse by the fact it was committed in the family home.
The sentence was backdated to 20 July, 2019.
The court previously heard the younger Camilleri, had struggled with mental health issues for many years prior to the horrific crime.
Prosecutor Tony McCarthy said the 57-year-old mother had been her daughter’s carer and was said to have been “overly protective and defensive” of her behaviour.
Jessica Camilleri was found not guilty of murder due to her mental impairment and was instead sentenced for manslaughter.
The court also heard she had stopped taking prescribed medication three months prior to the incident.
Two forensic psychiatrists had told the trial the knife attack was brought on by an intellectual disability and autism spectrum disorder that featured a fixation on horror films.
Jessica owned eight copies of The Texas Chainsaw Massacre and five of Jeepers Creepers.
In a victim impact statement last month, her older sister Kristi Torrisi claimed the family had tried helping but she had refused treatment.
“(Rita was) killed and butchered like she was nothing, all because of a fit of rage,” she told the NSW Supreme Court sentence hearing in February.
Jessica had previously attacked her aunt, pulled people’s hair in public, and made hundreds of threatening calls to strangers.
However, her mother believed her love could protect her from the world, the court heard.
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