I am so very sorry for your loss, it is so hard to get over losing a beloved pet. I know exactly what your going through. Our Lab/shepard mix had a stroke and our only option was to put him down. He was 14 years old and it happened overnight. That was almost 3 years ago and it does get easier.
Just remember you were holding Pixie and she died feeling your love.... Maybe she waited to say goodbye so when you picked her up the sound was her goodbye to you.
Take comfort in knowing she will be waiting at Raindow Bridge for you.....