The fact that she put in a book for all to see tells you how little she knows about the American mindset. It doesn't matter what reason she had for killing the dog. Some dogs are mean and probably should be put down. That doesn't mean you should announce to the world. Especially if you are in the public eye.
It should be noted I have a mean dog. He's been aggressive since we got him as a puppy. We just warn people that if he's outside don't get out of the car because he's an asshole and he bites. We took the responsibility for him when he was a puppy and so here we are. He's 12 years old now and we are just waiting for him to die.