Draco had been about to say something, fully expecting the Hufflepuff girl to dart off and try to avoid him. When she started coming toward him, though, he didn't quite know what to say. Usually they ran, and he was struck for a moment that she was incredibly stupid and brave for a Hufflepuff, and then he found his voice.
"Attempting to slink into the stones of the corridor doesn't actually work once you've been spotted by a Prefect, you realise?" He asked with a smirk, as soon as she was close enough to hear him.