Or is it something else?

Fleur came to Hogwarts to win the Triwizard Tournament and thought she hated the school before but she couldn't have been more wrong. With a mysterious D.A. class and its famously dangerous roster of murderous students; Fleur promises to not just take home the gold, but get to the bottom of "The Mystery of Hogwart's". Why Dumbledore allows such people to run loose in his school?