For women, the orgasm is 50% or more mental! FOREPLAY is vital to make a girl go! Play around, get her almost there, then initiate sex. Id also highly suggest for your girl to start masturbating and touching herself more often to find out what she likes and what makes her go. Sex therapists always suggest masturbation for these types of issues. Just remember its harder for most women to O then it is for guys, if she feels pressured in anyway to cum then its going to make it more difficult for her. A girl's mind needs to be clear and free of thought focusing solely on the act and being touched in all the right places to get off. Also, the clit has more nerve endings than any other sexual organ (male or female) and is the main way women get off. Try stimulating it more during sex, either her or you stimulating it and see if it helps. btw not all girls need to get off to enjoy the act of sex, im sure u make her just as happy either way