I would find out why she doesn't. She has some hangups that need working out. If she's willing to work with you openly and honestly then go for it. If she's not and has too many hangups and is not willing to help herself you have to move on. Most women especially young ones do not know about their bodies and what makes them tick let alone their mans. They must be educated. Start with mutual masturbation and foreplay. If she can cum from her own hand she will eventually be able to cum from yours. Once she can cum from your hand or mouth then it's a matter of moving to intercourse. Most men do not pay attention to foreplay and mood. She has to be aroused. Most women are uptight and need to be put in the mood through relaxation and then foreplay, if they are not relaxed they will not orgasm. Many women at first can only cum from either clitorial or internal stimulation. Some both but they need to learn if they can't. During intercourse have her or you stimulate her clitoris. Also you can get into toys to help her, such as vibrators on her clit. A dildo in her vagina while you are doing other things can teach you were she is most sensitive inside. Pay attention to her movments and sounds, how her body responds to what you do. Find out what makes her horny. Do you give her massages before you even touch some of the goodies? Do you tease her? Does she feel good about her apperance or is their underlining insecurities? Many, many factors to deal with, complex emotions. Learn to deal with them and help her learn to control them.