Surprise them.  More specifically, Malfoy. He was the one person in the house she truly despised. Sure, Blaise and Nott were death eaters alike, but they had shown at least  some redeeming qualities. Malfoy was still the same bully she had always remembered him to be. If she were going to find her way out of this house, she needed to beat him at his own game. He was the one determined to break her, so perhaps she would play like a snake. She would break him instead.