I agree she doesn’t know what she wants - I get the impression she might have been using you as a plan B if things with the straight friend didn’t work out. Even if she wasn’t, she didn’t prioritise you over them, which she would have if she’d been genuinely interested. It is really horrible to be treated as second best for someone else’s affections.
I’m really sorry this happened. I would definitely not contact her, for now at least.
And, really listen when people tell you who they are or what they feel - she told you she had feelings for someone else. I totally understand why you ignored that, you probably didn’t want it to be true, but she was kind of warning you she wasn’t totally invested.