Ms Wynn-Williams claims that in the mid-2010s, as part of its negotiations with the Chinese government, Facebook considered allowing it future access to Chinese citizens' user data.
"He was working hand in glove with the Chinese Communist Party, building a censorship tool…"
'Ms Wynn-Williams says governments frequently asked for explanations of how aspects of Facebook's software worked, but were told it was proprietary information.
"But when it came to the Chinese, the curtain was pulled back," she says.
"Engineers were brought out. They were walked through every aspect, and Facebook was making sure these Chinese officials were upskilled enough that they could not only learn about these products, but then test Facebook on the censorship version of these products that they were building."
Most Facebook executives didn't allow their own children on Facebook - according to Ms Wynn-Williams. "They had screen bans. They certainly wouldn't allow them to use the product."
And yet she says reports from 2017 - that the company had been using algorithms to target and categorise vulnerable teens - were true.
"The algorithm could infer that they were feeling worthless or unhappy," she alleges.
The company - which also owns Instagram and WhatsApp - could, she claims, identify when a teenage girl had deleted a selfie on its platforms, and then notify a beauty company that it would be a good moment to target the child with an advert.
Ms Wynn-Williams says she "felt sick" at the thought and tried to push back, "although I knew it was futile".