TambiPamby , It sounds like she did better when the stud wall was in place in her stall. Why not replace the solid wall??
I have seen laid back horses climb the walls of the stall because of too much, too many supplements. The overuse of supplements can cause the horse’s metabolism to run on extra high and as a result the horse is burning calories and dropping weight 24/7. Some horses are very sensitive to various supplements. Have you spoken to your vet? She could be sensitive/allergic to certain additives in your supplements .
What about a chicken or dwarf goat as a companion.