It's not enough to make Stefan back away, his own emotions twisting with River's, entangled in such a way that he can't tell which ones are his and which are hers. Maybe it's because he was just inside her head and that connection hasn't completely diminished. There were instances when if one toyed with the mind of another enough, a residual bond could be formed and accessed for a while, like when Damon had compelled Caroline from afar when he'd locked his brother in the cellar.

"Shhh," he soothes, stroking her hair with one hand. "I'm not, but I'm here."