I have the exact same policy. I would also suggest pull-up over underwear. You also allow training pants so I don't see her issue.

That all being said I am struggling right now with one boy. We have been in pull-ups FOREVER!! His 2 older sisters trained using pull-ups but he just doesn't get it. He will poop in the potty but he will never tell me he is wet. They don't use underwear at home at all. He is 3 soon and I really think if we just did the switch he would get it. Unfortunately I am not prepared to be cleaning up pee all over my floor. I guess we just keep at it and eventually he will get it.