A former inmate who reportedly spent time with the convicted mushroom cook killer Erin Patterson has shared insights into her behavior while incarcerated.

Speaking to news.com.au, the anonymous former inmate revealed that Patterson is attracting significant attention at Melbourne’s maximum-security women’s prison, where she has been held for 19 months since her arrest in November 2023.

“She’s intelligent, but she’s also entitled, arrogant, demanding, and rude,” the ex-inmate claimed.

Having spent over a year in prison with Patterson, the former inmate maintained detailed diary entries — and one entry, dated July 27, 2024, mentions Patterson’s estranged husband, Simon, and provides insight into her true feelings toward him.

“Erin despises her ex-husband and has openly confessed — she has made remarks that regardless of how long she stays (in prison), she will kill him,” the former inmate said.

Patterson is currently awaiting sentencing while in custody. (Credit: Nine)

During Patterson’s extensive trial — which concluded with a jury convicting her of three counts of murder and one count of attempted murder — text messages exchanged between her and her former husband were presented as evidence.

According to the former inmate, guards searched Patterson’s cell and discovered two bottles of mayonnaise and a chemistry book filled with notes on natural remedies.

“This is something I documented in my notes,” the former inmate stated.

“I was conversing with (another inmate) and asked if I could borrow her mayonnaise.“ She just laughed and joked about me ‘poisoning it like Erin Patterson did’.

“I was like ‘What the hell?’ and she recounted the story about how prison officers found mayonnaise in Erin’s cell that was allegedly used to poison [one of the inmates].

“She went to medical and was vomiting profusely. She was saying that the mushroom lady’s cell was searched and they discovered chemistry books with tagged pages.”

This follows accusations against Patterson of attempting to poison an inmate, but a justice department spokeswoman stated: “There is no evidence to support any claims of contaminated food or suspected poisonings at Dame Phyllis Frost Centre.”

Patterson’s pre-sentencing hearing is set for August.