I agree. Start with a ROMANTIC--RRRRRRRRROMANTIC, not sexual--setting and tell her how much you love her and appreciate her staying with you. Tell her about every little thing that you love about her, focusing more on her personality and interests than her body. DON'T bring up sex--don't even THINK about it because she'll pick up on it. Cuddle with her some and then when she's relaxed start kissing her in innocent areas, lips, ears, neck etc. She might tense up, expecting you to go right for the more sexual stuff. If you sense her pulling away a bit, back off. Just work your way into it slowly. Take an entire day if that's what it takes. Hell, take an entire weekend if that's what it takes. Make sure she's comfortable before doing anything remotely sexual. And make it ALL ABOUT HER. Put aside all your frustrations, don't get upset if it doesn't happen instantly. If and when she relaxes enough for you to focus on other areas of her body, KEEP YOUR COOL and don't go straight for the hot spots.
I also wanna say that women are intuitive. Scarily so sometimes. Your feelings about possibly dumping her because of the sex are probably getting through to her. If she feels like sex could ruin your relationship, she's not going to be likely to enjoy it.