More than two years after her very public exposure and disgrace, the spectre of Belle Gibson still strikes fear into her former associates, even those who once called her their friend.



Or so found the writers Beau Donelly and Nick Toscano when researching their new book about the wellness entrepreneur’s astonishing downfall, The Woman Who Fooled the World. The two journalists had done some of the earliest investigative reporting on Gibson, revealing in 2015 that the young Instagram star, who claimed to have healed her own brain cancer solely through diet, had raised substantial funds for charity with the help of her hundreds of thousands of followers – and then had not donated the money. The revelation led to increased scrutiny on the health claims that formed the foundation of Gibson’s wellness business, which included a cookbook and app named The Whole Pantry – claims that quickly began to fall apart.

Beau Donelly: ‘People thought she was lying. It only was believed when she was sending her story out online.’ Photograph: Chris Hopkins

But when Donelly and Toscano went hunting for the full facts from Gibson’s colleagues and friends, including those at Apple and Penguin who had lent Gibson their organisations’ huge commercial clout, they found the process was like pulling teeth.



“Her name was poison,” Toscano tells Guardian Australia. “I can’t think of another story I’ve covered that’s been so difficult to get people to speak to me.”



“We were shut down by dozens and dozens of people,” Donelly says. “We were threatened with lawsuits by others. It was incredibly difficult.”



Gibson herself declined to be interviewed and, though the authors secured some key on-the-record interviews – including talks with Gibson’s grandmother and estranged mother – many sources only agreed to speak to the authors anonymously and only after extensive negotiation, even those whose association with Gibson seemed innocuous.



The phenomenon that emerges in The Woman Who Fooled the World is deliriously complex and multifaceted: a combination of faults both individual and institutional, and of social trends both centuries old and very, very new. “There’s nothing new in cancer scamming,” Toscano points out. “There have always been snake-oil salespeople. There have always been people like [Gibson]. But where this story differs is her explosion to success, and her incredible reach was made possible by a number of intensely modern forces.”



Nick Toscano: ‘It’s hard not to think that the shaming of Belle Gibson crossed a line.’ Photograph: Justin McManus

These forces include the rise of a wellness industry that, in its worst manifestations, has become dangerously untethered from best medical practice. This is coupled with the emergence of social media and online “influencers”, and seismic shifts in the media industry that have radically changed how the public consumes news.

“The way information flows has changed a lot,” Toscano says. “The Gibson story is a really good example, I think, in the sense that she flourished and developed 200,000 followers without ever having gone through the checks and balances that are provided by traditional media.”



At the time of The Whole Pantry’s public collapse, “fake news” was not yet the meme-ified concept it became in the wake of the 2016 US election, but it was evidently on Toscano and Donelly’s minds as they wrote their book. Gibson’s story does seem to reflect some essential quirk in online media that facilitates, if not encourages, the spread of misinformation and untruth.



“Pretty much everything Belle had said about her varying illnesses in the years before she took to Instagram to post about having terminal brain cancer wasn’t really believed,” Donelly says, and the authors draw on testimony from old friends and classmates that paint Gibson as a habitual fibber. “People called her out on it, people thought she was lying. It only was believed when she was sending her story out online. And her whole business grew online.”



Just as Gibson’s rise exemplified some of the worst habits of online media, so did her downfall. Donelly and Toscano draw on the British journalist Jon Ronson’s 2015 book So You’ve Been Publicly Shamed to explore the violent outcry – including death threats and the circulation of her personal information – that accompanied Gibson’s fall from grace.



You don’t want someone googling your name and having it come up against Belle Gibson’s Nick Toscano

“Her scam was so against the norms of society that it does deserve condemnation,” Toscano says. “But when you delve into the social media damnation that she bore the brunt of, it’s hard not to think that the shaming of Belle Gibson crossed a line.”



Donelly says: “Ten years ago her public shaming would not have happened to this extent. Everything about this story is extreme.”



The book captures the spread of the Gibson phenomenon but there’s still a sense that there are depths yet to be plumbed. The specifics of her personal pathology will probably never be publicly revealed, along with certain elements of her biography, and the involvement and culpability of her various friends and associates as The Whole Pantry scam took flight.

“Like any story, all the facts aren’t available,” Donelly says, “and we can really only run with what we can substantiate. I think there are so many unanswered questions.”



If parts of Gibson’s story are still murky, it’s because the same people who refused to ask questions of her as she rose to prominence now refuse to respond to questions about her in the aftermath of her disgrace.

“People don’t want their names anywhere near hers,” Toscano says. “Young people who are among Belle Gibson’s age bracket – her group of friends and business partners – are more aware of their online footprint now. You don’t want someone googling your name and having it come up against Belle Gibson’s. That digital footprint is very hard to erase.”



Many of her associates are still operating in social media and wellness industry circles today, a fact that lends a self-interested air to their refusal to account for Gibson’s meteoric rise. “There’s a hesitation from some of those people because any scrutiny on the industry that they belong to is bad for business, and bad for them personally,” Donelly says.



“I think a lot of these people have some things to answer for. A lot of them took her story hook, line and sinker, and they endorsed her, and they partnered with her, and they used her – and she used them.”

• The Woman Who Fooled the World is out on 13 November through Scribe