"Well, as you so eloquently put it, my dress is "so tight’, there just wasn’t room for anything at all", she gives him a little nonchalantly shrug before whisking off as quickly as she could down the stairs.  Draco had never felt conflicting emotions like it, on one hand it was torture knowing she was naked under that sinful dress, and on the other he was incredibly turned on that she was in fact naked under that dress.