Ultimately, what the hell did it matter what Brandy said? Does Brandy's unfounded opinion of you mean anything? No, it doesn't, and your mother and girlfriend should have restrained themselves from making a scene over what is essentially nothing.
In other words, they should consider this a lesson in restraint.
EDIT:
I don't recall if Brandy was waiting on your mother and girlfriend, but if that was the case, they simply could have eaten their food and let no tip at the end. Tips are all about the level of service and they were dissatisfied with their waitress (if she was their waitress).
In other words, they should consider this a lesson in restraint.
EDIT:
I don't recall if Brandy was waiting on your mother and girlfriend, but if that was the case, they simply could have eaten their food and let no tip at the end. Tips are all about the level of service and they were dissatisfied with their waitress (if she was their waitress).