I'm sorry to hear about your loss Susan. May I ask how old she was?
Behind my house there is huge green area where some locals grow vegetables and other plants and it's filled with stray cats. It is a true cat paradise due to the amount of small animals such as mice and even reptiles and sometimes birds they use to prey. Four years ago one of the cats among others that we used to feed regularly, had a litter that, for some reason, early developed a respiratory illness. All of them. Two of the kittens died a few days later, remaining other two. Little more than a week had passed until both seen their health deteriorate for what I discovered later to be pneumonia. One of those days I went to visit them and one was in the middle of the concrete floor, near some old furniture, stumbling and breathing fast. I knew he was not well and I hurried to take him to the nearest vet, with my hands, without any box or anything. I was thirteen years old at the time and as you can imagine I was in panic. Everything fell apart when I arrived at the door of the vet and he was not there. I knocked and nearly kicked the door. In my innocence and abstraction, I was expecting him to come to my aid somehow. Meanwhile, the kitten - true unspoiled beauty - hastened it's breathing until it heavily sighed one last time. I can not explain, but I felt at that precise moment life disappear into the nothing, and leave there in my arms, still, the body of an animal that I swear could be the true synonym of physical perfection. I cried and cried as never before, right there in the middle of the street with it still in my arms. I will never forget that moment. Not only because of what happened, but because it marked a turning point in my life where I decided to never eat meat again. Veganism came recentely. I started to value all life and only find it sad that for such change to take place, that animal died. I still find it funny how such small creatures can change us so deeply. The other kitten also died, during the night, likely the same way.
Just wanted to say that I relate to your loss and know exactly what you're going through.