Boy! I don't envy this situation you're in at all. It sure could be working out better for the horse. I fear that this horse's feets are falling through the cracks.
IMO, she's gone past needing a trim to needing a rehab process, boots and pads included.
Where's she spending her time? Cause its rotting her feet. What does the rest of her body look like? She needs a darn good set up trim and a few whiteline treatments followed by continued thrush care and a farrier more often.
She has skirted flare at the ground edge because the wall is torquing outward...same as you growing a long finger nail, bending it backwards and walking on it. It hurts and you can take this pain away immediately with a bevel. So, you have to grow flare off the foot, but you can disengage it immediately. This flare has not been disengaged, which is why its gotten worse and no doubt, more painful.
She is also flared forward on long heels, which is not optimal back to front balance. This pulls the hoof forward, out from under the horse's descending weight and all parts and pieces...frog, bars, sole, white line and wall shape all pulled long like a clown's foot and not telling the truth on where they should be anymore....flare forward. This one takes time to remediate and the key to both, is the bevel and keeping it maintained and staying on top of the trim in order to move forward. The thrush is a biggie as well, or your spinning your wheels. Nothing can build, when its being eaten away. She needs more attention.
No, I don't envy this arrangement. It seems that the BO gets to advocate for the horse, for her friend, while the money comes out of your pockets. I really hope you are not over some kind of barrel here.
Was it not worry that brought you here? The only one that can advocate for the horse in the human world, is the one that truly loves him. By posting this thread, have you not done just that....trying to advocate for this horse? Now there's a source of relentless power and nobody should ever, ever have to feel helpless ever! Know your heart. Are you sure this horse can't come home? Tell me not what you can't do, but what you can make happen in the interest of her welfare. Does one not rescue in order to improve a horse's lot in life?
Aw, man! Just about every pathology in the book with thrush leading the way. I couldn't survive this way. My advise is the same as before. Either get her to call in the farrier right away and go there every day to treat for thrush, or take her home, call your own farrier and still treat thrush every day. The health of her hooves are both your responsibilities.
These hooves are a perfect example of why you can't judge a hoof by its cover. The "real" story is on the solar side.