If the text Jeff Dean wrote below is overwhelmingly true, I'd agree that she resigned rather than was fired. I suspect that it is overwhelmingly true as I'm fairly sure that Google legal would have reviewed it and ensured they didn't say anything falsifiable and likely that this paragraph is entirely true.

> Timnit responded with an email requiring that a number of conditions be met in order for her to continue working at Google, including revealing the identities of every person who Megan and I had spoken to and consulted as part of the review of the paper and the exact feedback. Timnit wrote that if we didn’t meet these demands, she would leave Google and work on an end date. We accept and respect her decision to resign from Google.

Notice he doesn't say she resigned immediately.

Do you believe she fabricated Megan's email?[1]

[1] https://twitter.com/timnitGebru/status/1334364735446331392