You know I saw in a movie once (don't remember which one and don't know if this is even true) but anyway, this guy was trying to give his wife an orgasm. That is what the movie was about. Strange. But, she felt pain also when she got close. For her it was psychological, but he also needed to learn to be more tender, patient, new skills etc.
But again, it was a movie so who knows.
Anywho, keep in mind that the clitorus is very, very sensitive. You cannot apply very much pressure to it or it does hurt. It may not hurt right away, but within a minute or two it will. Be very gentle and when you get a good response keep doing what you are doing. (lots of guys when you let them know they are doing well will start doing something else and it is so frustrating that it is impossible to orgasm after all of that)
if she still cannot climax after all of your and her attempts then maybe she should see a doc. It could be a disorder, or it could by psychological also.
Either way, try to convince her to seek help with it because she will enjoy sex a whole lot more if she learns to orgasm!