She woke promptly when the potion wore off, rendering her alarm clock unnecessary.  Her body didn’t feel rested, which was probably due to the nightmare and the potion.  She hadn’t screamed in a nightmare since just after the Department of Mysteries fight.  While they were on the run she’d had the dreams, but even in sleep her brain seemed to know it wasn’t safe for her to make that much noise, so she just didn’t.  She wasn’t looking forward to finding out if that would be a regular occurrence.