My mom use to get that way when i was a kid. Sweetest woman in the world till she had like 6 double margaritas. Then all hell broke loose. My dad just stopped going out with her, but then she found another man and they separated and then the reseccion came and they both lost their jobs so i had to drop out of high school to help support the family... but thats another story. There is really nothing you can do short of you going to get her drinks and make sure they make them weak as hell or when you can tell that she has had her limit to leave. She has to admit there is a problem before there is anything you can really do.
Its not the size of the dog in the fight, its the size of the fight in the dog...