Im going to say its her left hind. When she is goin in the circle counter clockwise, you can see her dragging and hesistating on that leg... especially between 2:36-2:38. And when you first switch directions... when she is on the far side of the circle you can almost see it give out. If its not that leg... maybe she has some damage from counter balancing to keep weight off the one leg... and its just going to take time for all the muscles in all the other legs to go back to normal.
Many people have sighed for the 'good old days' and regretted the 'passing of the horse,' but today, when only those who like horses own them, it is a far better time for horses. ~C.W. Anderson