It was before push back but after most loading was completed. She selected the fellow in front of us and he appeared genuinely surprised and delighted to have the fairy godmother pick him! This led another passenger to lobby for his Mother to be upgraded. It worked. So I am guessing about the nature of her selection but it seemed to be quite random. And with only one person moving into PE it didn't seem to have been done in order to accommodate other requests or seating needs.