I have a feeling you are seeing more to it than there really is. She's trying to make it work with a seemingly rocky relationship, but it must be worth it to her. I don't get the sense that there's anything there beyond a friendship between you and her. If you've already talked about being bi and poly, and she didn't take that as an opportunity to say she's interested, I would let it go. I think you may have simply let yourself get carried away by your fantasies.
I am curious about this statement:
Right now she is still with her bf, so I don't know if she's just messing around or if she is trying to find an opening.
I mean, if she were interested in you, why couldn't she also be with him? You have someone else.
But that's a different matter. My gut is telling you to leave it alone. I mean, you "fell in love" on the phone, right? There's got to be more than that for it to be real. Plus you might just be rekindling old romantic notions you have about your "first crush," which very likely is just a friendship in her eyes and nothing more.