I feel like I have been trying to get to the show ring for 20 years… I read your post and my heart breaks for you. It sounds like you love your horse sooo much. I understand because I am there too.
What I have had to do is not expect anything from my horse. You have done so much for her and you know you have. Even if you had all the money in the world it doesn’t sound like she would get better.
My advice is - enjoy her. No miracle injections or shoeing… just basic balanced trim, a good diet and a big stall to roam around with friends.
Feed her, love her and watch her. If you cannot get her comfortable with the basics maybe a conversation with your vet… I know it stinks… I am putting down one of my horses tomorrow that I raised and it - - - stinks! He has navicular, hock spavins, sacro injury, bone on bone in a hind leg.
Horses are beautiful and powerful animals but so very fragile.