Dear, from your profile, I could understand you are a Bangladesh national. Its good that you are going to class to learn some thing worth which is to develop your skills. Focusing, following or proposing a girl etc., keep after study completion. By and large, once she rejected your offer, why don't you stay away from her. If you are not desperate to go to class, stop, don't bother others. Sorry to say, It looks, she has matured mind more than you.