I'll raise a point that nobody has. At what point will this eventually begin to make you ill? It's really admirable that you are standing by this girl, but you are opening yourself up to an emotional nightmare. Somebody mentioned the word toxic earlier. Sadly, that can and has been me in a relationship.
Do your best by this girl, if you chose to take that path. But please, don't let this girl make you ill. There's plenty more fish in the sea.

An angry response might be indicative of an elevated mood, or be part of how she communicates when she's somewhat annoyed with people or a situation. Yes, the sad reality is, I believe that she is genuinely pissed at just you, as you have quoted her as saying, perhaps she sees you as her biggest obstacle right now.

When she said she thinks that you are "controlling her" and "using her for sex" - it seems to me that this is genuinely what she believes, at this point in time. Whether or not she can see things from a different perspective if she addresses these issues in therapy, I don't know. It's possible, if you aren't controlling, that her opinion of you won't change. I put this out there, for no other reason than really I've only heard your side of the story, I haven't heard hers, and there is always 2 sides of any story. So I can't pin point behaviours that have lead her to believe this (unless her psychosis made her believe this, which would be unfortunate).

Here's how I view this whole argument over the waitress - how about a different spin on it. What if she gets irritated when you pass remarks that "people hit on her". Maybe she doesn't sort of see it this way? She's a waitress not a (*insert word to indicate intentionally have men hit on her). Maybe she's annoyed that you even pass her comment, after all, she's doing her job, and customer service, in order for her to survive in such a cut throat industry requires polite and courteous conduct at all times (which in your eyes now may be interpreted as her being 'possibly flirty' - resulting in your perception of men hitting on her ..... leading her to calling you 'controlling' because you're indirectly accusing her of flirting (even if not stated) that causes the men to hit on her .... when she's just out there to work and earn money ......

I agree - mania has disasterous consequences at the best of times - so I'm really glad that you've pointed this out to her, it's important that she hears from you she could lose a lot more if she continues on this path. Her wanting sex after what she went and said? Sadly, yes, mania ... high sex drive ... ughh that's a hard one for you.

Finances, drugs, not affording her rent .... no wonder you're stressed to the max gee who wouldn't be! That's hard because I know how much you care about her and you're looking for answers as to what happened in the relationship / what possibly went wrong - I think most people ending a relationship seek some kind of clarity, and for you, thrown in the mix is the manic episode further complicating the issue.

What if you never get clarity?

What if it just so happens she will completely mess this up, despite everything you've done in her power to help her?

I merely put this out there, because that is a small possibility that that may be the eventual outcome, and if it is, you need to start working out how you will mentally cope a few months down the line, if that is the case.

Having said that last paragraph, I need to state something. Mania symptoms can be managed by mental health professionals. It sounds to me like she is in need of a lot of support by mental health practitioners. She's got a multitude of factors going on and it's not getting better and nor is she making things easier for herself, her current behaviour is making her likely consequences worse. And it sounds to me like she is simply too sick to realise this. She needs help. And I'm glad that you're trying to support her. It might soften the blow when her manic episode has passed.