In that instance I would have told her once you were sorry and didn't realize she wasn't done and that next time you would ask permission first. If she continued screaming at that point I would say we can talk more when you're ready to be calm. It is hard when someone has major mood swings but she essentially threw a tantrum and wasn't able to calm herself down. You apologizing to her over and over was feeding into her stream of being victimized. You didn't deserve to be screamed at for making a mistake. I'm sorry you had such a rough day but if you really think back there were probably very rough times when she was your sweet little 3 year old as well :-)