If Daisy had been aware of the exchange at the entrance to the dorms she would have made it perfectly clear that her twin was allowed in Slytherin, especially when she was present in said dorm. As it was, she was too busy searching amongst her many piles of books scattered around her bed. Yes, she could have summoned the book, but that would just send multiple piles crashing to the floor.
"Aha!" Daisy popped up from her hands and knees, the book on fifteenth century Venetian jinxes clutched proudly against her chest. "I am going to fucking murder that Defense essay. Ha, Mooney. Ha."
As the door opened, Daisy twisted around as she pushed herself to her feet. "You know nothing, Evan Potter," she retorted as she flopped back onto her bed. "I was just sitting here getting ready to study. Innocent as a lamb."