You can see by the sweat pattern that there is little contact in the middle of front to back. She needs a swayback bad to help even out the pressure. You can try going along her midline toward her navel and see if she will lift her back. Some horses get annoyed at first but you can get her to lift some. This helps strengthen her topline. If you go to youtube, maybe equine massage there are videos that show you how to get the horse to lift.
I never thought about that! Thanks, my aunts brother actually does equine massage :)