I think my best friend's girlfriend wants me.
Do you want her too?
Yeah, I want her because she is easy to sleep with.
If the signs are true and she does want you, you shouldn't succumb to her influence. Cheating is never okay, and you have to be the better man and look for another woman. Your friendship is worth way more than a one night stand.
I can't help it, I love sex.
I understand, but sleeping with your friend's girlfriend is only going to cause problems. I suggest that you steer clear of her if you want to preserve your friendship.