Taking care of those older horses can be expensive. If you can't afford to keep her at your current barn, then look for something more affordable. I'm not sure what your time constraints are, but what about a self-care barn?
Really, the way I look at it, if you have an unrideable horse, your only options are to find a place that is more affordable or have the horse PTS.
PITT BULLS ARE NOT THE ENEMY. WE ARE THE ENEMY. Shorty Rossi