I have a "busting theory" to inform you of. She tries to bust because she cares. She thinks that whatever her brothers do is dangerous and that they could eventually get hurt. She loves them and she does not want anything to happen to them. Maybe that is something that will be revealed in the last episode of the show (along with Doofenshmirtz going back to Charlene, realizing that he is not really evil). So, the more she fails, the more worried she gets, the crazier she gets.