If i had been instructing this ride, I would have been continually saying : 'SIT UP!! SIT UP' Her legs are too far back behind the vertical line of the stirrup leather, so is opening the front door and putting on her spurs too much (if she was wearing them), instead of using the calf. Every check of the horse in open country tests her forward balance. I have found this at this time in the USA including their military this continual leaning forward which wasn't so in Europe.