She was expecting the force of the impact. It was how vampires interacted with one another. Or at least it was how new vampires interacted and to Rebekah anyone younger than five hundred or so was a new vampire. She allowed him to pin her and she smirked slowly at him before just as quickly pushing him against the tree and holding him there.
"Because I could," she said. "Because you needed it. Because you weren't done yet. Maybe I just like you. Do you wish I hadn't?" she asked him curiously. Her grip on him was tight but not so tight that he couldn't move. She knew that he needed this, needed to stretch his new legs and see what he was capable of.