Cherish your memories and smile through your tears. She is one of a kind, never to be again, and helped make you who you are. You carry part of her through the rest of your life. I am so sorry for your loss.
I am facing the same problem within the next two or three days. My 17 year old Apache Cat is declining quickly and will need the blessing of euthanasia very, very soon.
Warm fuzzy hugs and positive supportive energy on their way to you.