No criticisms from me, either, just so sorry you are in this situation. You are obviously the sort of person who continues for better or worse with a situation. But there comes a time when if riding your horse is no fun - and after all this time it is not a hasty decision - it is crunch time.
There are horses that are confidence givers and there are horses that are confidence takers.
But some riders have the derring-do to ride almost anything and this gives the horses something to trust and hold on to.
Her age and issues make this a tough one, and I do hope you come to some resolution. Whatever it is, do not beat yourself up about it and know that it takes time to get over giving a horse away, or making other decisions.