Haven't been in that exact situation, but it does sound like it may be wise to back up a bit and give you and her some space. Maybe tell her that you have a crush on her, but you know she is straight and respect and value her too much to jeopardize your friendship in any way, which is why you need to back off a bit.
Honesty can be the best policy.

I think if you feed the obsession, you could be headed for trouble.

The good thing is that you are aware of what is going on with you and you do respect and value her enough to try to find the best course of action.