Nancy--I am so sorry to hear that you and your beloved Lucy are in such a terrible place right now. In my adult life I have loved and lost four beautiful dogs and as I think about them now tears are in my eyes.
Two died suddenly and unexpectedly, two died because of the choices I made for them.
This is how I made that choice: I believe that is my privilege and my responsibility to share my life with these wonderful creatures. I know that they trust me 100% to care for them and to do always what is right and what is best for them. I try to do for them what I would want someone to do for me.
I would not be quick to give up on my dog, but if I saw that she was suffering and there was no hope of her turning the corner, I would let her go--as I would want to be treated if I were her.
I think the reader who urged you to believe in miracles might have been thinking that Lucy was a human. We tend to be less compassionate with human members of our family than we are with the furry ones. This past month I watched my friend's mother struggle to die for two days after she had been removed from life support. I would NEVER allow that to happen to my dogs.
Good luck to you,dear. You and Lucy will be in our prayers tonight.
Marty