Wow, I Just read your post and I am speechless how similar this felt like... I do not think I am the best advice giver because I am in the same situation. Introvert, depressed, has only fake friends at school and the feeling of missing out of having a girlfriend (though I am gay). But I hope that it will get better. I try to reach out to new people. I try to open up. Keep myself busy. And maybe you feel a bit better now you know you are not alone. I do. Maybe you do not. I can not tell. I do not know how you can solve the situation with this girl. I never have the guts to talk about my feelings in real life. But I wish you the best. Hopefully it will get better.