Anne, I imagine that both people and dogs can't help comparing the new life to their lost Sofie. Having said that I know nothing about your particular issue.
I just wanted to say, based on 1 standard Schnauzer and 2 GSD, the breeds are pretty different in character, as I'm sure you know. David had a Schnauzer when we got married-and she was simply not a people dog. She was polite, greeted people, ate, excreted, and watched-but had none of the handler devotion of our GSD. OK, big generalizations from 3 dogs, for whatever good it does.
What is the new pup's name?