Thanks to all of you! It really helps to get other perspectives when stuck in a situation like this.
I think you're right, and that not attending the vacation (while very appealing) isn't really an option because it would be the nail in the coffin of my relationship with my parents. On the other hand, I have assessed the cost of leaving the vacation early, and it seems like it would only be a few hundred dollars. We don't really have any extra money laying around, but we could swing that if we had to. Really, can you put a price on your sanity?
I also think that you're right in that I should just ignore everything. I really don't want to talk about it, I don't think anything is going to be resolved, because my father will simply back up my mother regardless of how ridiculous she is. In turn, she's not going to admit that she had anything to do about the matter. Therefore, I lose regardless.
It's funny/ironic, because in all of the conversations that I had with my siblings, they counseled me to talk with her and deal with it. My response to them has always been that "this ends badly for me, I can see to the end of it, and I KNOW how it's going to turn out." Ick.