Oh Julie, I just read this and I'm so so sorry. Your story brought tears to my eyes. We all understand your loss and how painful it is. I just wish there were magic words to make it better, but there aren't. You knew when the time was right for her to go and you did a kind deed when you ended her pain. God Bless you for giving her peace and may God give you peace in your heart.
Give little Lucy lots of hugs because it sounds like she is grieving too. Maybe she will help give you peace.
God Bless