I would look at her quality of life now. Pain is not the only consideration. If you were me, you would make the appointment to have her put down. You would tell the kids that it is her time to go to heaven and be with thier Great Grandpa, and let them say good bye. Amd you would be at the vet and hold her while she slips into forever sleep, letting her see the love you have for her and knowing that she will be in a better place. It is so hard to do, but it isn't right for our animals to suffer. I put 2 dogs down in the last 2 years, I had them from 7 weeks old, and I still cry for them.