My wife has continually told me that I am not the cause of her issues. She said that the hottest guy could be in bed with her and she would still have no desire to have sex.
My wife once complained to her doctor about having ZERO libido. Hearing her say that did not phase me one bit and at the time I was much more concerned that her other health issues be addressed so that she could become as healthy as possible. As for her "zero libido" I knew that I could manage to work with that.
So how does one approach a partner that has zero libido and improve their interest in sex? You don't! You work on other things and then as things improve you learn that your partner's sexual response is much different than your own and has likely been healthy all along.
SCIENTIFIC HYPOTHESIS #1 - Women only experience sexual pleasure in the form of an evolutionary jackpot. Because we are all made up of the same parts, just arranged into different places, women also get to enjoy the urge to orgasm which is only critical in procreation for the male. (This is recent research, not old school and close minded crap). Essentially woman have orgasms for the same reason men have nipples.
SCIENTIFIC HYPOTHESIS #2 - Sexual pleasure is derived from personal development and validation. Some of us want to please others, and some of us want to be pleased. Some of us have never learned how to be selfish and others have never learned to be selfless. For those in social work doing the most selfless jobs, it is very well know that you can not help others unless you can first help yourself. Sometimes it is actually the most difficult for one to learn how to be selfish, simply because they don't feel deserving of anything. Personal development in a marriage with regards to learning how to be better at both being selfish and selfless improves sexual wellbeing.
SCIENTIFIC HYPOTHESIS #3 - Everyone's sexual response is DIFFERENT! Most often the model of what is required from a male in order to successfully procreate is mistakingly used by both men and women as a standard model of what sex should be like. Because we are all made up of the same parts but put together differently, many women grow up thinking they are sexually broken when comparing themselves to a male and may never understand that they are actually perfectly healthy and capable of something perhaps even more profound sexually than a male because they grew up comparing themselves to the wrong model of sexuality.
SCIENTIFIC HYPOTHESIS #4 - Everyone is healthy exactly as they are.
perhaps you just need to keep a very open mind and help your wife discover herself sexually and learn to appreciate that she may very well be healthy just the way she is. Perhaps she enjoys too much being selfless and always helping other and meanwhile never caring for herself. An easy way to teach her to be selfish is by allowing HER to help you, even if you don't need help! It will give her a sense of purpose and belonging, and then you can teach her that she also has to help herself as well before helping you.