This entire set of tweets is talking of an incident that did not happen recently. There's no record of her calling her manager an asshole in public while she was working there.
Well by exposing your manager you are essentially calling her an asshole (lets assume the manager is female, why not).
Perhaps you are not aware of the fact that the person tweeting no longer works at that company anyway, having changed employers a while ago.
It's not about the tweets, it's about publishing the Excel sheet of salaries. That's bound to piss off her employer, so why should they give her a bonus?
She specifically says that she only told friends about the bonuses being withheld
Huh, she published an excel sheet of salaries, claiming to expose injustice. That's saying "fuck you" to her managers, and to Google.