There's a wonderful little bit of writing called 'Rainbow Bridge' floating around on the net, if you've never read it...I recommend it...it'll make ya cry...but give you hope that perhaps one day you'll see her again.
I was hit pretty hard by the loss of my beloved ginger cat 'William' (Also known by a multitude of nicknames, including but not limited to Kaiser Wilhelm II
) who left this world purring in my arms at the vets.
Lizzie sounds very well loved, and at least she went peacefully and in the home she knew and loved. My thoughts are with you.