Their gentleness toward her is set up earlier, when we see her being affectionate with the dogs, and their loving response to her. It seems she's the only one who goes to visit them, to pet them, to be kind to them.
As for their hostility to him, well, dogs aren't that stupid. Of course they couldn't understand exactly what the doctor was doing, but they knew that he hurt them.
"And you could have it all. My empire of dirt."

But was that ending credible? There was nothing to indicate that the doctor had done anything to cause the dogs to be hostile to him (they wouldn't know or understand what he used them for) and there was nothing to indicate that they were vicious. It just struck me as highly improbable that they would attack him but not attack the daughter who released them.