Your problem is difficult, it really depends on you. Do you think you will only be able to be friends with her? Because it sounds like she doesn't want a relationship with you. If you can hold on to the hope that maybe some day things will be different then you might be able to stay friends with her. However there is the possibilty that all you will be is friends which sounds like it will be really difficult for you, if she is a valuable friend to you try out just being friends and if it becomes too difficult talk about it with her and explain how you feel.