I went to leave and she started in about money and bills. I said if she wanted to do it we can do it now.
ERRRNNNNGGGNNGGG!!! -- wrong.
This is where you lost it. This is NOT "dropping the rope."
Better:
"If you want to talk about finances, we'll do that very soon. I'm not going to do it when you're being rude and accusatory, and I need to get to _________ anyway (GAL activity). I'll drop D11 off at 7." (or whatever)
You did pretty good sticking up for yourself during the confrontation, but it's a confrontation that never should have happened. She's going to try to drag you into these multiple times, about finances, mostly, so that she can play the martyr and see if you'll come-a-rescuing.
