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.
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?