To be perfectly frank, what you've described doesn't sound like a viable relationship at all. First, if she's not medicated and is bipolar, she's not in shape for one (having been involved with bipolar women, I can say that without meds they're in no good for relationships). That she has no sexual interest in you is apparent by her unwillingness to schedule surgery (for years!) to make it possible. And that she's not been willing to commit to a relationship for years also indicates she's not interested in one with you (and, yes, poly folk commit themselves to relationships).
The repeated "we should just be friends" is more than a subtle clue as to what's going on. She's not interested in you as a serious partner. You're just a roommate she spends time with because she hasn't had any serious romantic relationships.
So, are you wrong for being hurt? No. It's always painful to find out that somebody we're highly attracted to isn't attracted to us in the same fashion. I think the only wrong thing you could do is try to maintain a relationship that's never really gone anywhere. Being poly isn't a method to allow you to hang on to a partner who isn't really interested; the need for serious attachment is as strong in poly ties as mono ties.