Stefan returned the smile, and gently pulled, subtly indicating that she could move against his chest and lay against him as she wanted.
If Elena had really been his slave, he'd be treating her very differently. But she wasn't his. She was his brother's, and therefore, although Damon hadn't invited him to explicitly, he was, to some extent, playing "Daddy Dom" to Damon's "Big Bad Dom." It was something they'd done before, but it'd been years. It had the benefit of getting a slave acclimated to different types of submission, and testing how they responded to each.