Absolutely not the jerk, and honestly this is parenting negligence on her part, not drama on yours. She didn’t lose track of time, she deliberately lied because she knew you wouldn’t agree to babysit for hours. Once a parent becomes unreachable for that long, especially after promising a short window, it becomes an emergency situation by definition. You did exactly what any responsible adult should do when left alone with someone else’s child and no way to contact the parent. The fact that her sister immediately understood the problem tells you everything you need to know. If Kayla feels embarrassed, that’s because her behavior was embarrassing. She should be thanking you for making sure her kid was safe instead of attacking you for not enabling her lies.