Welcome to PC, Starks518!
Her behavior you describe here is classic Borderline. We can't diagnose, and I'm not saying she doesn't have bipolar (maybe she has both, dunno), but of what you describe, I don't see bipolar in it. But I see nothing that isn't Borderline.

The reason I say this is because it may help give you insight. See, for a long time, my BF's borderline behavior confused the heck out of me, but once I knew what was actually going on, it was easier to understand (and not take personally. Well, as personally ).
Here's a link
Borderline Personality Disorder Symptoms | Psych Central

One of the biggies you're seeing in this situation is the idealization/devaluation symptom. And it involves very black and white thinking. All or nothing. The 180 degree turn. In this kind of thought pattern, there really isn't middle ground. The important thing for you in that is understanding that it's NOT YOU. You did not suddenly become any of the things her meanness threw at you. So do not take them to heart (easier said than done, I know), because they do not reflect reality. They do not reflect who you are. The only thing they reflect is her distorted thinking. Which is almost undoubtedly contributing to your depression, because we think mean things about ourselves in depression, and it feels like a confirmation of those things. IT ISN'T.

You can't fix her. She'd have to really want to do that. For herself. Since no one wants to be told their perception of the world isn't accurate(!), it's not very likely she would seek help in the first place. Or see the need for it, as it's "everyone else" causing the problem. Also, it takes a lot of hard work on her part.

The drama's not helpful in your managing your BP, so best advice is to learn from it and leave it at that.