Perineum(muscle between anus and genitals) is important area involved in orgasm. If it is tight and insensitive, orgasm may not be possible. Massaging her perineum will help to reach orgasm. You can take care of clitoris by CAT( coitl alignment technique) If she does female deer exercise. she will improve her sexual health. Deer exercise for man and woman is different. Many gynic problems will be solved with this exercise.
For women a large part of achieving orgasm involves getting in the right mindset. You might be doing all the right things, but if she isn't into it then it's not going to happen. If she's getting stressed about having an orgasm (or about anything else) then it is distracting from the pleasure itself. It is also a possibility that she has started a new medication recently that could have this as a side-effect (anti-depressants especially). Try lengthening foreplay - touching all over the body without getting to the good stuff right away - and spend time doing romantic stuff that you both like (a good meal, favourite movie, etc). Talk about what turns you on together and get a good sleep!