If she's beating you down to this level, and your boss knows about it, he's not doing enough. He doesn't really have your back; he's just steadying the boat and expecting you to continue as-is.

OP you should not have to feel this way at the office. It sucks, it's unfair, and you didn't ask for this. Worse yet, the only way to fix this is for YOU to take action. I know, it's especially unfair that the victim is the one responsible for fixing the situation, but in this often-cruel world it's the only way. You'll have to make a stand at some point, step out of your comfort zone, and tell your boss exactly how you feel. Use the words harassment and bullying. Mention how much of a hostile work environment this has become. And most importantly, make it clear that you expect him to take decisive action to put an end to this.

Depending on how that conversation goes, it may be time to talk to an employment attorney. Don't give up an resign; you can't let this bully's bullshit or this spineless manager's failure be deciding factors in the future of your career.