I think you are just being very hard on yourself...

You obviously made an impression on people, not just the teacher... Accept the fact that you did better than you thought you did, and move on...

Don't feel guilty because you would have marked yourself harsher than the teacher did... Be thankful and if it bothers you that much - be more prepared next time...

As for your the girl in your class.... eff her. If she doesn't like it that you did better than her, that's her problem not yours..

Just my two cents...