> If she didn't do it and they don't have good reason to believe she did, then she could and should easily win a large lawsuit against them, since they have publicly accused her of illegal activity.
Despite the popular refrain of “truth is an absolute defense” in the context of defamation law, in US law falsity is an element of the tort, which means that the plaintiff bears the burden of making a prima facie case that the accusation was false by at least some evidence, the defendant doesn't bear the initial burden of showing that it is true or reasonably believed.
Also, there is a very good chance, since Mitchell was publicly involved in the controversy over Google's firing of Timnit Gebru before Google made the accusation, that Mitchell would be found to be a public figure within the context of Google's alleged defamation, which would heighten the requirement from falsity plus harm to proving actual malice.
Also, if Google is lying, they almost certainly also spent over a month building a constructed evidence trail and doctoring records to support the lie between the very public lockout and the actual firing.
So, no, winning a defamation case wouldn't be easy, wouldn't be quick, and wouldn't fail to be extremely expensive in litigation costs.
Plus, every step Google takes on this is just resulting in more of the remaining people in the affected area of the company going public with problems, and it’s not like Mitchell seems to be hurting for alternative employment so as likely the only value of winning the lawsuit would be a PR poke in Google's eye that they are getting on their own anyway...why bother?