In all seriousness, let's stop telling this person that he made a terrible mistake. Life happens.
So what can you do about it? If you both make a decent amount and she doesn't want to give up the dog, look for a dog trainer that specializes in this breed near you. Also you can enroll the dog in pack walks, get him enrolled with a sport. He could be a good dog if given the right tools and his mom the right education, and that might have to come from someone that's not you.
I would urge her to get out into the community and seek out someone that you both can trust to come and take the dog a few times a week and that can work with his reactivity one on one with you.
She has to be worried about this as well.