Thanks for sharing this experience. Honestly I don't know anything about any of this really. It's all well beyond my level of comprehension. The one thing in all of it that makes sense to me is the part where your friend told you the two of you are toxic for each other.

Was she using you? Well... I don't know if she did so intentionally. But from what you wrote it sounds as though she probably did, at least financially if nothing else. Was she afraid you liked her romantically? Again, from what you wrote, it's unclear to me what either your friend's or your intentions were. It sounds as though there were a lot of mixed messages passing between the two of you. Is she mentally ill? I don't know whether or not she is mentally ill. Your friend certainly does seem to have her problems though! What could be the possible reason? I'd have to say again I just really don't know. But, at least from my perspective, what caused all of this is perhaps of less significance than is the question of where you go from here.

It may be helpful to try to understand your role in this so that you can avoid getting into a similar situation with someone else in the future. And, hopefully, you're seeing a counselor or therapist with whom you can delve into that. But, beyond that, it seems to me what is important is to leave this relationship in the past, learn what you can from it, & go on with your life. There is a danger here, I think, that you could get stuck in this toxic relationship & just get pulled down deeper-&-deeper by it to no good end.

My best wishes to you...