I know how you feel... and it's not good just now.
My wifes dog that we'd owned since he was a puppy had to be put to sleep a few years ago.
His life as an old infirm dog wasn't happy and his eyesight had gone too.
Took us all ages to get over the loss but eventually we did... never forgot him though ! and there are still pictures of Glen around the place to remind everyone that he was a great dog in his day.
Try to remember the good times when your dog was young and fit and happy I'm sure that's what she would want.
SG