I can't keep my horse any longer, I am now a full-time caregiver for my husband and have no help with him or the care of the horse.?

I am 73 and the work is never ending with my husband and hauling hay bales and water buckets is pushing me over the edge. I barely have 10 minutes a day to take a shower. I just can't do it all. What do I do? I have contacted horse rescue agencies and they are no help as they are already overcrowded. I won't sell her as she is likely to get shipped to Canada and sold for dog food (yes, that IS happening now) I am really considering just having her put down, she has had a wonderful life with me and my husband and as she ages I don't want her life to get worse. I would rather see her dead than abused. I am so desperate, I need help, please, someone give me some ideas. I am in tears just typing this question. I am at a breaking point. Help.....