Alot of times for a woman it is all mental. As in they have to be relaxed and almost want to orgasm. See if she will do the DJ Diddles while you have sex with her.
As with the mental thing try to clam her down or try to find out what stress or work/life problems she has and try to take the problems out of her life for a moment in time.
Nice dinner and relaxing night then have fun at home.
In the end a womens orgasm is all about her and how she feels. Don't feel down about it.
If you two use lube try to get the extra stim. type for her it may help. Some have a little menthol (I think it is?) in it and makes her area completly sensitive to what you are doing.
Tried it with my wife and she could not stop orgasming.