Tell me what should I do..??

I like a girl very much. She too likes me. But when I proposed her, she said me no. Reason behind this was, that her parents wont allow this, and love marriage is not aloud in her family. I tried to convince her alot and also said that I will talk to your parents, but she is still on that only, that her parents wont allow. I dont know what to do. She said me that u have to forget me. We had a small fight on this. And now we dont talk. We see each other, but behave as we are strangers..
Guyz help me with this I love this girl..
And I cant stay like this..without her.