Can you guys tell me what happend over here?

I dont want to sound harsh when i say this, but it sounds like to me that she has caught on to your attraction to her, and it makes her feel uncomfortable. Maybe she wants to go for the other kid that likes her, i wouldnt know. But it sounds like she is handling the situation a bit immaturly..you sound as though you were a great guy to her. Maybe she could have been using you at the end for the class, im not sure about that either. But it sounds like to me you arent going to get anywhere with her relationship-wise. Wish her a happy birthday, and see what happens. It will be hard, and if you think you can do it, try to not text her until her birthday. Let her think you forgot all about her, let her miss you, then just pop out of nowhere with a happy birthday. If she has any positive feelings for you at all, this will be very sweet to her and let her know that you care about her and that you remembered her birthday. take it slow if she answers, if she doesnt, then i would say just move on.