I loved that video...I am not a riding expert but I do know horse language. She was not in discomfort, in my humble opinion, she was having a blast.
I don't have working speakers, so not sure if you could hear music, it looked like her tail was very rhythmic, not sore acting at all. I really enjoyed her sense of fun, and their partnership was phenomenal. Personally, I think the rider was there just because, the mare was having all the fun...she was/is a ballet horse in that performance.
