The woman spoke of her "reckless" plan when the long-running inquest into 15-year-old Annette Mason's murder resumed for a one-day hearing on Wednesday in Brisbane.
Annette was bludgeoned to death in a house she shared with friends in Toowoomba, west of Brisbane, in November 1989.
No one has been charged over Annette's death.
The inquest heard the woman, who cannot be named for legal reasons, contacted police claiming to have new evidence in 2025.
She claimed a suspect told her previously undisclosed details about the brutal murder while they were living together.
The woman consumed podcast episodes and news stories about the cold case murder before seeking out a suspect, Queensland coroner Terry Ryan heard.
"It was a friendship that sort of just went into a relationship," the woman said.
Under questioning by Mason family barrister Clem van der Weegen, the woman agreed she was "trying to solve this murder" herself when she sought out the suspect.
"Yeah, I was just so reckless," the woman said.
"Today sitting here, I'm proud of what I done.Â
"I know that it is a big risk and I know my life could have been ended any time but I just took it in my own hands."
Annette's body was discovered in her bed, with the cause of her death found to be blunt force trauma to the head inflicted with a piece of timber found in the laundry.
The woman testified she talked about Annette with the male suspect, who cannot be identified for legal reasons.
"He kept calling her 'she'. He said she was bashed before she got to the house," the woman said.
"Then she was hit around the head."
The man had previously claimed innocence of the murder, Mr Ryan heard.
"He said it was a copper that had killed her. He said 'that's why all the evidence went missing and they're just trying to put the blame on me'," the woman said.
The woman was asked what impact the suspect's alleged words had on her.
"Clearly he had killed Annette Mason. He had done that," she said.
The woman denied her claims were based on details previously available in podcasts and news stories.
The suspect also gave evidence on Wednesday at the hearing attended by Annette's mother and siblings wearing t-shirts printed with her image.
He described the true-crime-podcast-obsessed woman as a "nutcase" and testified they had only a friendship.
The suspect said the woman's claims were "absolutely not" true and he "would not have a clue" why she made them.
"She was good to hang around with - a good friend," he said.
The inquest into Annette's death was initially closed in 1991, only to be reopened in 2018 after pressure from her family.
Hearings were last held in 2022.
The inquest will spend the next several months receiving written submissions.
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