If you think she got arrested for trying to break up the fight, then you're missing the point the way she did.
It was never about her tussling to break something up. It was about how she pushed and hit the cop once he arrived to break things up. You NEVER EVER touch cops. Especially like that. You will go down every single time, no questions asked.
He let her off light with a disorderly, which is, at most, a couple of hours in jail until she get bond and a small fine. She would've gotten more sympathy had she just took the L with some self-awareness. Instead, drunken emotions ran wild and she embarrassed the shyt out of herself.
As someone in a high position of power who was humiliating fired for "incompetence", the last thing she needed was go viral because she threw a drunken 3-hour temper tantrum. No amount of press conferences, etc is gonna save her law career, which is in serious jeopardy.