Is it an event that you like to attend. you don't have to NOT go just to spite her. I have gone to events with W and not exchanged a single word with her. Heck, I do it every weekend at synagogue (probably should not have said heck and synagogue in the same sentence - also a bit punchy today). bottom line, go if you want to go. Don't worry what she wants.
I like your phony response because it is sincere and what you were really thinking. Too bad we can't use it
RAI
P.S. Way to bike! That's what I'm talkin' about! I have a run date with friend at 9PM,weather permitting.