Ok, as you know, I know next to nothing about training, but putting together earlier comments about the socialization of the little ones by mom and the fact that you had to bring Princess Sophie home so young due the circumstances, is there another, older dog nearby that you trust with whom Sophie could have play dates that might help in teaching her bite inhibition? I understand this would all be contingent upon vaccinations, etc, and I don't even know if that would be an appropriate intervention, but it is just a thought. Of course, this would be in addition to the training you are doing at home. Just tossing out ideas, here...
