My 2 1/2yr old is basically potty trained she tells us when she needs to go and everything barley has accidents ( we use diapers for bedtime and naptime, and sometimes long car rides only) but when it comes to undies she has constant accidents and everything.. She wont tell us when she has to go when she has them on we constantly check every 15-20min if she needs to go but still decides to go in her undies instead ( we’re also working on pulling the undies down to show her)

Any tips on how to help her with the undies and showing her we don’t go pee pee in the undies?

TIA