
They don't actually
need milk once they're weaned. Your friend should stick to the breeder's advice - if she starts fiddling with his diet she could cause stomach upsets which could make him very ill, especially such a tiny breed.
Changing homes is very stressful for a puppy, and a temporary loss of appetite is quite normal. If she offers him the food he's used to (she could soak it in a little warm water if she wants) and he's drinking, then I'm sure he'll get his appetite back as he settles is.