Victoire Weasley could quite possibly be described as evil. Teddy had told her to be out of the bathroom in time, and she'd considered complying, but then she realized that she didn't really comply for anyone. She couldn't be sure, but she figured that was at least part of what attracted Teddy to her in the first place. So given that thought, being out of the shower in time would be a disappointment for him. She couldn't disappoint, now could she?
So she'd waited until shortly before Teddy would be home and turned on the water, stripping down her clothes before stepping into the shower. When he called her name, she had her head under the shower head, the water running over her hair, making it impossible for her to actually hear him.