When Hermione reached the door, she turned to bid them goodbye and saw Severus was standing up, too. "Oh, please, don't follow me," she said. She noticed her voice was slightly pleading.
"Hermione, please," Severus said quickly and quietly.
"No, I just... I want... need to be alone." She slipped out of the room. Shutting the door behind her, she leaned back against the closed door and squeezed her eyes shut. Tears threatened to come out if she didn't calm down. She wasn't sure, but she knew she was scared.
She was scared of her nightmares more than she would ever let on.