It sounds like you've done all the talking that you could. I don't know if you've tried this and didn't mention it or if you just haven't thought of it but what have you done to make her feel relaxed? Just trying to talk her into having sex won't work and by what you're saying, it sounds like you're gonna have to put a lot of effort in to get what you want. Dan and Jenn just recently uploaded this video to YouTube and it goes through the relaxation process before the actual intercourse happens. You can try doing some of these and see if that changes anything. Good luck!
YouTube - Orgasm Tip #1 - Find Out Why Relaxation is Crucial...