Need help with girlfriend problems in bed (explicit)?

My girlfriend and I just started trying fingering, although this is not her first time. Once she is properly self-lubricated, I rub what I'm assuming is her clitoris and her reaction is great. Her legs shake, her breathing gets deeper and she begins to moan; shes says she loses control of her body. But she has never had an orgasm because she becomes too tender and always motions for me to stop. What can I do to get her to have an orgasm? Are there other techniques that uses other parts of the vagina that would help? What should I do? She really deserves this because she is the most wonderful person in the world and this would be a nice repayment for her awesomeness. Thanks for any help/advice