So far as hydro therapy, you may want to check out if there are any animal science universities and such in your area? Here, we have Texas A&M university, and their large animal facility has the water rehab get up there. (I don't know about Michigan, though).
I don't think I'd have the ability to give up my horse, but then again, I have my own place with land to keep her on, and I don't have to board her.
I hope you are able to get her fixed up, either way, you at least seem like your being responsible in both her abilities and yours, so kudos there.
Perhaps if she is well trained (and behaved), lease her out to someone learning how to ride and work with horses to cover costs? Someone that doesn't plan to compete or do strenuous activity?