What RP said
The truth is you already do have feelings for this woman, which may be why you are so drawn to want sex with her. You may just be someone who can't do casual sex, you may need that emotional connection first.
I would not use this woman to satisfy your need to experiment, instead keep her as your close friend. My husband has a close friend that for years we have all called his other wife. There is no sexual relationship and I think if that was added it would destroy what they do have (mostly due to her background and issues).
Just out of curiosity are you comming from a strong religous background?