Have you tried just cutting out the diapers all together? She clearly has no problem doing what she is supposed to while on the potty - even in a diaper. Sometimes you've gotta push the undies thing and then praise her for what a big girl she is wearing them. Kids usually don't like the feel of pee all over them in undies and they are more likely to start using the potty at that point. She's at a perfect age where she should understand, just sounds like she wants to do things her way