Gibson gathered a large social media following and released a cookbook and app called The Whole Pantry, where she told fans that she'd eschewed traditional cancer treatments in favour of "clean eating" and juice cleanses.
But in April 2015, she told The Australian Women's Weekly that her claims were false.
"No. None of it's true," she confessed. "I am still jumping between what I think I know and what is reality. I have lived it and I'm not really there yet," she said.
"I think my life has just got so many complexities around it and within it, that it's just easier to assume [I'm lying]," she said.
"If I don't have an answer, then I will sort of theorise it myself and come up with one. I think that's an easy thing to often revert to if you don't know what the answer is."
Gibson told The Weekly she had a "troubled" childhood, which may have led her to lie about her condition.
The young mother - she has a son called Olivier - said that as a 5-year-old girl she had been forced to care for her mother, who has multiple sclerosis, and run the household, while also looking after her autistic brother.
But Gibson's mother Natalie Dal-Bello said that's not true.
"What a lot of rubbish," Mrs Dal-Bello told The Weekly, saying the only truth to the story was her MS.
"Her brother is not autistic and she's barely done a minute's housework in her life," she said.
"I've practically worked myself into an early grave to give that girl everything she wanted in life."
Mrs Dal-Bello said she had not been in touch with her estranged daughter for years and was unaware of her success as a wellness blogger.
"I can't tell you how embarrassed we are about what she has done," she said.
"She just plucked bits and pieces of other people's medical problems and assumed them as her own. She had a heart problem growing up, but that was it.
"She doesn't seem to be sorry. There doesn't appear to be any remorse. I've never seen her cry in her life."
Ms Gibson took in more than A$1 million in profits from her cookbook and app.
Gibson's publisher, Penguin Australia, could also be implicated in the case.
Last year, CVA director Simon Cohen said Penguin Australia "had willingly co-operated with a concurrent investigation that examined whether the company had also violated" the Australian Consumer Law.
Mr Cohen said Penguin had admitted that it had not "required Ms Gibson to substantiate her claims prior to the book's publication" and "will make a A$30,000 donation to the Victorian Consumer Law Fund."
Last September, a shocking video revealed Penguin was concerned about cracks in Gibson's story. The video showed Gibson undergoing media training and mock interviews with Penguin publicists, and was asked to prepare for interrogation from investigative journalists.
"What we suspect might happen now is that because you are a success story of the moment - you are one of Australia's great success stories of the moment - you know what journalists do, they want to start scratch, scratch, scratching away," a woman said in the video, off-camera.
"They already are," replied Gibson.
"And we're concerned about that," the Penguin representative said.
In the footage, recorded in 2014, Ms Gibson is asked about the seriousness of her claimed cancer diagnosis, and cheers when she announces the cancer she claimed to have in her uterus has miraculously disappeared.
"I'm going to get tested for ovarian cancer. I no longer have cancer in my uterus," she says, raising her arms and letting out a "woo-hoo".
When pressed on when she was told the cancer was gone, she replied: "Not long ago, but it all still feels like it sucks down there".
During the training session, Ms Gibson is pressed on the "experimental" treatment she claimed to be taking, and the charities she couldn't prove she had donated to.
She struggles to explain the treatment, and says the Indonesia- and Cambodia-based charities she was dealing with "don't speak English", but that she could have documentation to prove her claims within six months, "once I get my s*** together".
The interviewer tells her to "get your story straight about the charities. I think they're going to go there with that".
The judgment will be handed down by Justice Debra Mortimer in the Victorian Federal Court on Wednesday morning.
