HappyGiant
Sounds like both of you are guilty of making a lot of assumptions. The communication needs a lot of work and should probably be top priority right now.
To be brutally honest, sounds like your W has some serious mental health issues at play. Getting physically ill on all major holidays, when sex is on the horizon, etc is her defense mechanism. And to make matters worse, you have conditioned her to respond in such a way because it works! So there are things you can do to stop this cycle. Stop rewarding her "illnesses" by "switching gears" as you stated and caretaking her so much. You will not be a terrible H for doing so. However, you will be making a big mistake if you carry on in this fashion because I can already sense the resentment in your words. That is only going to grow bigger if you don't break the pattern.
Hope that doesn't come off to harsh because I do not mean it to. Good luck tonight in whatever you decide to do.