I've been following this thread since it began but haven't said anything so far. I was wondering if it's because she rejected you that you're so interested in her (besides the fact that she enjoys sex so much
). She didn't need you, and I've noticed in life that's a red rag to a bull - we always want people who don't seem to need us back. It sounds like you've been chasing after her, and I think maybe she represents excitement, adventure and really wild times (TM), away from your current life.
I hope you don't mind if I mention something else. You've mentioned that your wife has some issues with sex because of her difficult past. Speaking as somebody who has been through similar things as your wife, I know that these things can be resolved. Rather than chasing after another woman you think may fulfil a fantasy, what about making a real effort to build some of that excitement and passion into your relationship with your wife?