I'm so so so sorry.
I think that people get really really "protective" of their dogs and if they feel they are in danger, some can lash out. No excuse. It sounds like normal dog behavior and play to me. No reason to be disciplined in the first place!
I once went to a dog park and the lady had a little Yorkie puppy and Jackson kept trying to play with him. He makes a lot of noises, grumbles, etc, when he plays and she kept saying "shoo! get away!" to him and it was really pissing me off but I never did say anything. Yes I would control my dog if he was being a jerk but the yorkie puppy was clearly LOVING it and kept trying to play back.
But anyways, dogs will be dogs. And that really sucks that it happened because I know I wouldn't trust my mom with my dog again, not alone certainly.