Oh Kimmie, you sweetheart you!! There's no way you can replace Lucy, but it's not wrong to bring another dog into your heart! I have 4 cats and love them dearly. They are each unique, their personality's are TOTALLY different! All my baby's came from shelters and each one was sick when I got them with one ailment or another.
You get that puppy and know in your heart that Lucy would want you to be happy. Hugs and Love, from one animal lover to another!! Darlene