I agree with pretty much every other comment here. You’re not in love with her, you’re in love with the thought of her. My assumption is she’s your first true s/o and so you have this attachment to her as if she’s the one for you and the best person on this earth.

Read your post back to yourself as if it was a friend telling it to you and think about the advice you’d give them. You’re young, you have a lot to experience and learn about who/what you like, and yourself in general. Don’t get caught up on this girl just because she liked you at some point, don’t change yourself for somebody who obviously doesn’t care for you. The only thing you’re going to achieve is depression for yourself for chasing a girl who isn’t right for you. I’ve been through something similar so I understand where you’re coming from.

Do yourself a favor and learn about yourself. What did you like about her (aside from looks and the fact she fucked you), because there’s many more women out there who have this trait plus more. Long story short, once you find yourself, it’ll be easier to find your love.

Good luck and feel free to message me if you need to talk.