It depends, because my mom doesn't get so upset about her mother talking crap about her as she gets upset about the idea that someone is putting down a kid's parent to that kids face. She doesn't think it's right for anyone to do, let alone her own mother.

So sometimes I don't say something because I don't want to see my mom get upset, or to hear some of the more outrageous things my grandmother has said. So sometimes I'll forget exactly what is said.. However I will on occasion share it with my mom and lately she doesn't have that much to say about it because she (reportedly) has never felt very loved by her own mother. My mom pretty much knows how her own mother views her, despite how wrong that view might be.

Do I talk to my grandmother about it? That is much less likely. That is because grandma will get upset that I was defending my mother. It'll get to the point where grandma complains to my mom saying "You're daughter is always very quick to defend you." Which my mom isn't surprised by at all, however grandma makes it sound like a bad thing...