I noticed the way the horse was standing as well, but she's a TWH. Isn't that sort of normal for them?
No, not to this degree :)
While Walking Horses do have a tendency to NOT stand square, there's a huge difference between standing "comfortably un-square" and "uncomfortably in-square".
Also, they are not prone to stretching out, as the OP's mare appears to be, unless something hurts. It's possible the mare has developed some ulcer or other issues from the long-term use of the serious meds she had to be on.
The OP's mare looks "uncomfortably un-square" to me. I think she could really benefit from a quality chiropractor who also does acupuncture:)
This is my other TWH, Rusty. The pic was December, 2017, making him 23-1/2 years. He is standing about as square as Walking Horses like to stand, unless I tell him to "square up". He is standing square, underneath himself, front and back as he should be. Even though one hind hoof is slightly ahead of the other it's healthy slightly ahead:)
He is only a tad bit splay-footed (toes out) but varying degrees of splay-footedness do indeed exist in the Walking Horse gene pool.
IMHO, both the OP's farrier and the vet are not clear as to what constitutes normal for a TWH and what does not ------which leads me to worry about how this pretty mare is getting trimmed. image.jpg