As far as I understand, doing that (recording meetings without notifying other participants) is a crime in California (https://codes.findlaw.com/ca/penal-code/pen-sect-632.html) and that justification does not make it permissible.

So if she admits that she did record these meetings without informing the other participants, then in this defamation case - a key part of which is about the claim in HuffingPost "She also illegally recorded internal conversations within Tesla without anyone’s permission, which is clearly criminal conduct" - she has a good chance to lose, as it's not defamation if it's true.