This was not Frances Haugen’s plan A. The Facebook whistleblower says she does not like being the centre of attention, but what she saw while working at Mark Zuckerberg’s social media empire compelled her into action – and made her famous.

“When I look at what I did, this was not my plan A. It wasn’t my plan B, it wasn’t my plan C. It was like my plan J or something,” she laughs. “No one sat me down and said ‘what I want you to do is whistleblow’.”

But that is what Haugen did. In May this year she left her position as a product manager at the social media giant and took tens of thousands of internal documents with her. The documents have triggered a maelstrom of allegations, including that Facebook knew its products were damaging teenagers’ mental health, were fomenting ethnic violence in countries such as Ethiopia and were failing to curb misinformation before the 6 January Washington riots. On Monday, Haugen will take her damning views of the company to Westminster when she testifies before MPs and peers. Meanwhile, Facebook spirals deeper into crisis.

Haugen, 37, says the turning point came when she moved in with her mother, who had given up an academic career to become a priest. “I am really lucky that my mother is an episcopal priest,” says Haugen, who was born and raised in Iowa. “I lived with her for six months last year and I had such profound distress because I was seeing these things inside of Facebook and I was certain it was not going to be fixed inside of Facebook.”

Her concerns over an apparent lack of safety controls in non-English language markets, such as Africa and the Middle East, where the Facebook platform was being used by human traffickers and armed groups in Ethiopia, were a key factor in her decision to act.

“I did what I thought was necessary to save the lives of people, especially in the global south, who I think are being endangered by Facebook’s prioritisation of profits over people. If I hadn’t brought those documents forward that was never going to come to light.”

Speaking to the Observer over a video link, Haugen displays none of the stress you’d expect from taking on a near-$1tn (GBP730bn) company with its ranks of lawyers and advisers. Haugen’s expansive and upbeat answers, sometimes punctuated with laughter, contrast with the measured performance she gave to US senators on Capitol Hill on 5 October in which she memorably accused the company of putting “astronomical profits before people“. It’s the kind of conversation you’d expect to have with a successful Silicon Valley professional working at one of the world’s biggest tech companies, which Haugen was until five months ago.

“We have intentionally not been doing many interviews, because it is not about me, it’s about the documents,” she says. “I don’t throw birthday parties because I don’t like being the centre of attention.”

Haugen says her friends and family have been supportive since she stepped forward this month as the source of a series of Wall Street Journal revelations based on her leaks. “A friend of mine, right before I did testimony, gave me this wonderful saying, which is what I repeat to myself when I have anxiety, which is, it’s not about you: you are the conduit for the documents,” she says.

Haugen says her new home, next to the Atlantic Ocean in Puerto Rico, helps. She is talking to the Observer from the Caribbean island and US territory in its capital San Juan, where she is afforded an anonymity that she doubts she would have been given in northern California.

“I feel very lucky that I live in Puerto Rico because no one has ever recognised me here.”

She adds: “I think if I was still living in San Francisco it would be really stressful because I am sure that people would recognise me there.” In San Juan, she says, it’s “a lot easier to stay sane. Here I can go for a swim or … I like to cook. I can go to any of the little markets and I just feel like a normal person. So it hasn’t felt like that big of a change, really.”

There are health reasons for the Puerto Rico move too. A decade ago she was diagnosed with coeliac disease, an autoimmune condition, and in 2014 she entered an intensive care unit with a blood clot in her thigh. She recovered, but still suffers pain from nerve damage in her legs.

Haugen admits she isn’t looking forward to the colder weather when she arrives in Europe, for a trip that includes her Westminster appointment on Monday and the annual Web Summit tech conference in Lisbon next week. But she is in huge demand and the documents she leaked continue to make waves, with a fresh release of reports into those memos by a group of media organisations including the New York Times, on top of the WSJ‘s initial efforts. This weekend it was reported that Facebook bungled its attempt to curb hate speech before the 6 January Washington riots and that employees repeatedly flagged concerns before and after the US presidential election, when Donald Trump tried to overturn Joe Biden’s victory.

The revelations have been relentless since the WSJ first started reporting on the documents and give the impression of a company that is unable, or unwilling, to combat the consequences of its huge scale. Facebook’s family of apps – including its main platform, Facebook messenger, Instagram and WhatsApp – is used by 2.8 billion people a day. With politicians and regulators on both sides of the Atlantic closing in, it has been reported that Zuckerberg will announce a rebranding of the parent company this week in a bid to put distance between his business and the revelations.

For Haugen, Zuckerberg is a big part of the problem. The Facebook founder and chief executive controls a majority of the voting shares in the company, which makes his position unassailable. That has to change, says Haugen, and she believes independent investors in Facebook would seek change at the top if they could.

“I believe in shareholder rights and the shareholders, or shareholders minus Mark, have been asking for years for one share, one vote. And the reason for that is, I am pretty sure the shareholders would choose other leadership if they had an option.”

Against a backdrop of revelations about Instagram’s damaging impact on teen mental health and Facebook’s failure to police rightwing hate speech and misinformation in its home market, Haugen says Zuckerberg has failed to show he can protect the public from the negative effects of his networks.

“He has all the control. He has no oversight and he has not demonstrated that he is willing to govern that company at the level that is necessary for public safety.”

In a statement Facebook said: “At the heart of these stories is a premise which is false. Yes, we’re a business and we make profit, but the idea that we do so at the expense of people’s safety or wellbeing misunderstands where our own commercial interests lie. The truth is we’ve invested $13bn and have over 40,000 people to do one job: keep people safe on Facebook.”

Facebook reported a net income, a US measure of profit, of $29bn (GBP21bn) last year.

The spokesperson added: “We have no commercial or moral incentive to do anything other than give the maximum number of people as much of a positive experience as possible. Like every platform, we are constantly making difficult decisions between free expression and harmful speech, security, and other issues, and we don’t make these decisions inside a vacuum – we rely on the input of our teams, as well as external subject matter experts to navigate them. But drawing these societal lines is always better left to elected leaders, which is why we’ve spent many years advocating for updated internet regulations.”

Haugen’s appearance in London on Monday is before the joint committee on the draft online safety bill. The proposed bill – which Boris Johnson has promised to fast track – imposes a duty of care on social media companies to protect users from harmful content, or face the threat of multibillion-pound fines from the communications regulator, Ofcom.

Haugen says she is still considering what to say about the bill but backs at least one of its measures, which requires companies such as Facebook to give Ofcom a “risk assessment” of content that causes harm to users. “I do believe in things like risk assessments. Facebook should have to provide articulations of what they believe to be the risks on the platform. Right now Facebook never gives us details about how they are going to fix problems.” Before she left Facebook, Haugen worked on the company’s civic integrity team which, before it was disbanded, had been tasked with monitoring electoral interference on the platform.

Haugen wants to see more “friction” introduced into Facebook’s systems, such as Twitter asking users to read a link before they post it, to have the Facebook platform embrace a chronological, and therefore less provocative news feed, and for greater transparency to be forced on the company. Facebook, and the huge amounts of data it amasses internally, must face regular and ad hoc scrutiny by regulators, says Haugen.

“There needs to be an avenue where we can escalate a concern and they actually have to give us a response.”

In the future, Haugen wants to start a non-profit organisation that supports this kind of social media reform. “These are the solutions that will protect people in the most fragile places in the world.”

In the meantime, she hopes that Zuckerberg and his senior colleagues listen.

“I have this hope my disclosure will be large enough, and give impact enough, that he gets an opportunity to say, ‘I made some mistakes, I want to start over’,” she says. “Because the point of moral bankruptcy is … saying you deserve a chance to start over, that we as a society do better when people get a chance to wipe the slate.”