I think had she not moved OK as she cantered away, Rachel would have pulled her up. And she moved fine.
Harry would not have been allowed to remount but it did look as though he had forgotten that rule for a moment.
Had the mare not been moving well, and she tried to jump, it would have been a disgrace. She had to get her speed up quickly given how close the last is and perhaps that looked out of order, but even so.