I really feel for you Karen. You are trying your best and nothing seems to be working. Have you received advice from your vet? Are there any palliative treatments which still may help her recover some decent quality of life?
If you have exhausted all options, it may be that her time on Earth is coming to an end, and the kindest thing is to let her go free.
This is a very hard decision I know. I ha dto make that ecision for my own dog when all I wanted was for us to be together, as we always were....
But do what is the most loving thing for her. She needs you and your bravery, right now.
Her love will not die. My own dog showed me that.