I'm not going to beat your up for thinking that you could successfully joke about this matter with her...that is so "me", but, for future reference, you can't successfully joke about this matter with her. And attempt to do so now that you have this knowledge, is (I hate this...) passive aggressive. Nuff said.
So, what should you have done when she demanded sex? Heather...you want to take this one? I think the only thing you could have done is exited the house. Get in your car and spend the night in a hotel, or in the car, or wherever.
My wife's stubborn, too, and I could see her doing this. That's what I would do.
But you didn't do that. And yeah, I can see that she might be pulling the smoking teen trick on you.
Man...this sucks. Go get some counseling for yourself...you need to just be able to sit in a room for an hour with someone and spill all this.