I think hvert is right. Separation is the only cure for obsession if she doesn't reciprocate your feelings. I have a close friend who has had the misfortune of several of her close male friends confessing their love to her, and when she did not reciprocate, they left her refusing to even be friends. She was devastated to lose them.
Most likely, this girl is going to want to stay close friends with you, even if she doesn't feel romantic feelings. So separating yourself from her will allow your feelings to cool, and maybe grow towards someone else, plus you won't be clinging to your friend, or forcing her affection, or worshiping her. **Make sure you tell her you are leaving and why before you do though. Don't keep this to yourself, bc it can only hurt both of you.**