Some times it can be the smell of the new puppy. She comes from a different home and was surrounded by different people/animals and at least with my dogs sometimes it happens that if the other dog smells "funny" they avoid him. When Mia was sick and came back from the hospital, Nina and Bambi didn't like her being near. They would smell her or my hands and go away. It took me a couple of weeks and baths to get their noses to accept her again.
