I understand that a man has a mitzvah of onah, to make his wife happy, does a woman also have such an obligation towards her husband? If she doesn’t really need/want marital relations is she obligated towards her husband?
There is an idea that a wife has obligations toward her husband, and it is wrong for a woman to abstain and inhibit her husband in this area. However let’s be practical, there is a reason why she is being this way, as it isn’t the nature of women to act this way. Chazal say that it is the nature of a woman to want to be with her husband, and it most probably is not because she doesn’t have a need, but because you are doing something wrong. I would advise you to speak with someone about this. If you would like to talk to someone please let me know.
Y:D 234-67, Rambam Ishus 15-18, Sefer Chassidim 506, 873, Darcei Teshuva Y:D 197-4, Shela Shar Haosiyos “Kedushas Hazivug”, Shevet Halevi 2 101.