We are sad because we miss them, but, after a while, we realize they aren't really gone ... not as long as we remember them and keep them in our hearts. There will always be a special place in your heart for her, nothing will ever take that spot.
Sometimes one will leave us so that another can have someone to care for it. I remember when my Lucky died (He was from the SPCA, too - he was found in the snow, almost frozen to death. He had pneumonia and they were fixing to put him down. Instead, I took him home. He was with me for many years.) He was injured, by a kid in the neighborhood (we think) but he seemed to hold on till I got home from work and he passed in my arms. I thought I would never want to have another cat, it just seemed to painful ...
A few weeks later, I passed by a house that had a sign up "kittens for sale". More than likely, had Lucky still been alive, I would have ignored it. But, I stopped to look. As I pulled into the driveway, I noticed a tiny kitten had slipped out of the fenced area and was headed straight for the busy street. I picked him up and he snuggled under my chin and fell asleep in no time. His name became Snuggs and we spent many happy years together.
Jo Ann