(ex) girlfriend is straight

So there's a girl I've been friends with since Fall of 2013. We slowly became friends, and then best friends, getting closer and closer over time. There were a few things we had in common that we originally bonded over, and then things we were complete opposites about--and that served as a way to look at things from a different perspective through each other.

Almost a year after we'd been friends, she said she had a crush on me. That she'd liked another female friend before, but it wasn't a big thing and she'd basically thought of herself as straight this whole time, so this was a new thing for her. Now, a few months prior I had realized I liked her, but was content to just push it down and ignore it, because of past experiences with crushes on friends. But after she said that, I told her it was mutual, and she got rly happy (and bashful).

A few months of flirting happened (some joke-y, but some serious--mostly on her end, as I cannot flirt worth a flip) and we started dating. Things were really great, and I fell completely in love with her. Again, though, she was the one to say "I love you" first. I imagined a future with her, and although we're both still teens a part of me seriously thought we'd stay together--or at least I really, really hoped.

Flash forward to a few months after our one year, and she's suddenly talking to me less and less, even distancing herself from our friend group, and constantly alluding to problems in her life, but never talking about them to me. I got quite frustrated with the lack of communication (something that had been a slight issue even early on--I felt like we talked about serious issues without her really talking. That's a bit beside the point though), and I was considering breaking up with her if, after bringing up the issue, nothing changed--even though the last thing I wanted was for us to break up.

Then, she sends me a long message, saying that she's straight and likes guys and "we" mistook platonic love for romantic love, and nothing changed after we made our relationship official. That everything she felt at the time was real (and yet nothing changed???), but she doesn't want us to be together anymore.

And I'm just quite blindsided, I guess. If she had come to me, saying that we'd grown apart, and she wanted to break up--that really wouldn't have been a surprise at all. As I said, she hadn't talked to me much despite me reaching out on multiple occasions. And if that was the case, I feel like it might have been easier to accept somehow. But after over a year of us dating, she pulled the "no homo" card and said she didn't actually love me like that. It's hard to deal with, yeah, but also slightly hard to believe?

I accept the fact that she says she's straight, because only she knows her orientation. I'm just frustrated and hurt, I guess. And we're still friends, of course, I immediately asked if we could remain friends and she was relieved that I wanted to. So we're talking. And I'm trying to be cool about everything, but she keeps bringing up old things like an anime couple she used to say was us, tagging me in relationship text posts and saying stuff like "this was so you", and it's just left me sitting here as I slowly turn into one big question mark.

And I'm not sure what I'm hoping to achieve by posting this, maybe just some insight, or maybe I need to rant a bit. Anyway, if you read this, thank you for listening!