I think the issue there was that the dog wasn't harmed. Was the dog interfered with? Could you articulate that the dog is now ruined based on that person's activity? So if you tip the dog over, or even if you come up and you flick it in the ear, you do something to negatively impact the performance of that animal to serve Diane's friend. Is that acceptable and would the law capture it?
I would argue that it would. Just because the dog isn't hurt, have you done something to terminate its career? Is it serviceable anymore? No, and this is where the interference clause might come into play. You didn't specifically injure the dog, but did you harm it? The dog can't work anymore because of what you did. I would argue that had to cause some kind of harm, or why isn't it working anymore?