She did mention that the mare was difficult even before her unjury.
If I found no signs of pain, either muscle/from arthiritis/ poor farrier work (this is what I find in most cases, so I shoe my own horses and have taken natural farrier school) I would probably start back from the beginning of training, communication, and try to get her heart in your hands before her hoof. The hoof is probably the MOST misunderstood part of the horse... besides mabye the digestive track lol...
I hope you are able to figure out what the trouble is!
