Malfoid tears the first page out and the book does not stop her, so Mione takes a fistful and the two of them empty it onto the floor.
Nothing happens. The door was never locked. It opens when somebody turns the handle.
MalfoidIt said the room would not let us out. It did not say that twice, and I did not check.
Corvina sits down on the rug and laughs until she has to stop, and says her grandmother would have been furious and that she is delighted.