I’m not taking her side at ALL, but I do think this is one of those situations where I wonder what would happen with a different approach. This is the source of 100% of my parents’ fights: Regardless of which party is right, you both put up the defensive. I just wonder what she would have said if your first response was, “Did the male babysitter bail on you?”

That said – you’re clearly in the right as she never asked and SHE is definitely the one who shouldn’t be jumping all over you. I mean, you’re the one catering to her need, she should be appreciative you’re there at all family or not.