One thing she could be doing is exagerating to teach. As you said this horse has only 3 days and does not know much. This is a method we use on our horses, or horses in training; exagerate to teach and refine as the horse understands. Yes, we started out, over exagerating the lean back to let the horse understand the weight shift. As time progresses, now you only need to roll your lower back and our horses respond to the shift in your seat. And although it is called reining, in my opinion the ultimate reining horse would need no reins at all. They completely respond to your legs and seat.
There is something about riding down the street on a prancing horse that makes you feel like something...even when you aint a thing - Will Rogers