Your aunt sounds a bit similar to AXH. I seriously think one of the reasons he's still drinking is that AA wasn't enough help for him. If I got it right, narcissists cannot fathom that the world looks different to other people than to them, and that they are actually not always right. That on occasion, they are even responsible for garbage that happens in their lives.
I don't know what to do about the uncle -- he's stuck between a rock and a hard place here -- but... he's also an adult. He's probably suffering, living with a shrew like your aunt, but then again, that's his problem, not yours. He may feel forced to side with her, but that's a decision he's going to have to make.