I wanted to make a couple notes.Our vets here know nothing about horses, just how to give them shots and take coggins. We are limited to only a couple of farriers in the town I am in. We will try to give her the best hoof care we can! Thank you so much for your advice!! I will see what we can do about farriers, because he does an awesome job on everyone else's hooves, just not hers, and I think part of it is because she isn't a huge fan of gettin her hooves trimmed, so he always cuts her session short. We have a hoof file, is there anything we can do with that to help a little In between trims?
Just because a vet is predominantly a cattle/pig/sheep vet they have to know something about horses. I think you're underestimating your vet.
Secondly, the fact that your farrier takes as little time as possible on this mare is a warning sign to me. They may not be paid to train that mare but they are paid to do a quality trim. You as the owner are supposed to make sure that your mare stands for the farrier. No excuses. Your "farrier" ought to be trimming your mare and charging you extra for the poor ground manners. They can and do get injured; size doesn't matter.
I trim my own minis (No I don't recommend it. I do it because a farrier isn't allowed on the property but I'm planning on becoming an AFA certified farrier when I graduate and have the money.) and it can take me an hour plus to trim one of my minis. In that time I am critiquing my own trim, soaking hooves, training my horse to stand for me, and actually trimming. (Soaking is a god send btw) I've had to deal with long hooves recently. It sucks.
Lastly, I would take a VERY careful look at your other horses' hooves. The problem may not be with just this one mare.