My main issue with this is that the way we train dogs is that we train them to be dependant on us. So yeah, she's training him to come out of his shell, maybe, but if it works the same way a dog does he'll only be loyal and listen to her. Especially because anyone else he meets won't treat him like a dog and will expect him to behave like a person without the expectation of rewards which would probably make him more adverse to others
Of course, he's a human being too so it won't go down exactly like that. I'm just saying that from the very first premise the way we train dogs is by training them to be codependant