A Sydney woman accused of stabbing to death her Scientologist father and teenage sister was suffering a psychotic episode and is likely to mount a mental illness defence, her doctor says.

The 25-year-old, who cannot be named, is facing two counts of murder and a third of maliciously inflicting grievous bodily harm with intent to murder over a frenzied stabbing at her south-western Sydney home on July 5.

The woman, who has been diagnosed with schizo-affective disorder, allegedly fatally stabbed her 53-year-old father and 15-year-old sister in a psychotic rage at the family’s Revesby home.

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Psychiatrist refers to Scientologists as flat earthers She is also accused of critically wounding her 52-year-old mother during the attack.

The woman was diagnosed with a mental illness late last year, and the court has previously heard she was denied follow-up treatment at Bankstown Hospital because of her parents’ Scientology beliefs.

She instead sought private psychiatric and psychological treatment and was prescribed medication, which she ceased taking in January.

However, her parents allowed her to restart the medicine three weeks before the stabbings as her symptoms worsened, a prior court hearing was told.

The woman on Monday failed in a bid to be released from Long Bay Prison Hospital into a locked hospital ward, with Magistrate Matthew Richardson denying her bail in Burwood Local Court.

Her psychiatrist, Richard Furst, said she had made considerable progress in recovering from her psychosis but continued to suffer from delusions and remained at high risk of suicide and violence.

She was one of only nine female inmates in the prison hospital’s population of 110, and was socialising with women who had substance abuse and psychiatric problems and established criminal histories.

Dr Furst said the very strict security, which included lockdown from late afternoon until early morning, limited visits and the wearing of uniforms was hampering the woman’s recovery.

Research resources on ScientologyHe asked Mr Richardson to release her on strict conditional bail to Bunya, a locked medium-security ward for murderers acquitted or declared unfit to plead on the grounds of mental illness.

Located within the grounds of Cumberland Hospital in Western Sydney, Bunya would provide greater support and allow the woman’s mother, uncle and siblings to visit, Dr Furst said.

“People recover better with their families, as do patients who are engaged with an active vocational plan,” Dr Furst said.

The woman was taking medication and had appeared before the Mental Health Review Tribunal. She was likely to mount a mental illness defence, the doctor said. The woman’s mother, who was one of her victims, also wrote to the court in support of the application.

Prosecutor Cate Dodds opposed bail, saying the woman’s progress was evidence the treatment at Long Bay was sufficient, including access to art therapy, craft and aerobics.

There could be no dispute that she had committed the material acts and her legal liability was yet to be determined by a court, Ms Dodds said.

“(The application) is, in our submission, premature given the high risk the accused stands to pose to herself and others,” she said.

Mr Richardson agreed, declining the application.

The matter will next appear in the same court on November 19.