In a strange way, her doing this makes her very sexy.
That's because if you think sex is bad, you also think bad is sexy. My 2bx consistently expressed desire if I in any way threatened to leave or find another man to meet my needs. I mean, everybody is this way to some extent. God knows, I have my own "bad boy" fantasies but you're never going to be able to function sexually in a "good" relationship if you can't figure out a way to appreciate a jolly, friendly f*ck or "play" at being "bad" rather than really living it.
Passion, Since your relationship is good except for the sex, I would suggest that you read "Passionate Marriage" by Schnarch. It's a thick piece of material but it might be helpful in your sich. The Schnarchian Bar Scenario might work for you if you can imagine yourself in the course of a normal loving non-sexual evening being bold enough to turn to your H and say "Since you are clearly not interested in meeting my needs, I'm going to go out to the bar and see if I might meet somebody who can. I would greatly prefer having sex with you so I hope that you will follow me to the bar and be the one who propositions me.". Theoretically, doing this sort of thing will have the same effect on your H that 12-51 experienced only after his wife had given up and decided to leave. The trick is that you have to be brave enough to do it but also feeling loving rather than angry or sad about your situation. Tough mental space to achieve. Then you basically have to wash/rinse/repeat until just a little hint that you might head for the bar is enough to get him aroused. I am taking great liberties and greatly simplifying what Schnarch has to say with this example but I really think it might work for you.
"Tell me, what is it you plan to do with your one wild and precious life?" - Mary Oliver
