I am asking for a friend. Her dd will be 3 in jUly and wanted to wear underwear on Monday. She went with it. Her dd knows when she has to go and says peepee so they go but then she only releases a little bit and jumps off. She won't fully empty her bladder. Then she had an accident b/c she can't hold it. She did poop on the potty today.
She's tried everything. M&m's, toys etc.

Any advice on how to get her to fully empty her bladder?