Nelliesdad, so sorry to hear about your devastating loss. We here are all now, or have been, going through the same unbearable grief. It's impossible to describe to anyone who hasn't felt it. I think what Sil said is so true, that it hurts so bad because they follow us through their entire lives, depend on us, until that one moment they say goodbye. True companions.
Do not feel bad or self-conscious about your grief. It doesn't discriminate by size or gender. It means that you had a deep, deep connection with little Nellie, which is so obvious from the care you gave her throughout her life and in her passing. Knowing when to let them go is part of loving them, though it causes us so much pain.
I too have been through things in my life that one would think were the "worst ever"... but losing my two cats has really been the worst. It's that one-on-one bond they have with you and no one else, staying by your side through thick and thin. We are so blessed to have them.
Please keep posting stories about Nellie and let us know how you're doing. I will keep you and Nellie in my thoughts.
"How it is that animals understand things I do not know, but it is certain that they do understand. Perhaps there is a language which is not made of words and everything in the world understands it. Perhaps there is a soul hidden in everything and it can always speak, without even making a sound, to another soul." ― Frances Hodgson Burnett