I too agree that your mare is feeling alot better! About 6 years ago my mom bought a tb mare who was pretty malnourished, but was bomb proof! After she got some weight on her she turned into a new horse, bucking,biting, spooking! No grain either. Anny way it took alot of work because the horse wasn't as bomb proof as she thought, just exhausted!
I also think that your mare is moving differently because of her lack of shoes. It doesn't take them long to get used to them but it seems to take a while after you take them off.
Good Luck and I would recommend as much exercise as possible. Even if you just lead her on walks and lunge her.