Oh! I have a really good one! This occurred when my Mimi (mom's mom) was about 72.
Mom and Dad are divorced, but Mom has always been close with Grandma (Dad's mom). When she died, Mom, Sis, and I were all heartbroken. The funeral was about an hour away from home. We all rode there with Mimi, who also knew Grandma and was fond of her.
After the service, Mimi began to get really snippy with Mom because of a situation that has been dormant and in the past for a good five years. I was about 12 and on the verge of tears all day. I looked at Mimi and said, "Mimi, this is my grandma's funeral. I can't take you going on and on about it. Please shut up and you can gripe some other day." Not the nicest response, but I feel I was excused, it being Grandma's funeral and all.
Apparently Mom and Sis made similar comments--your comments are inappropriate for a funeral and we can talk about it another time. Mimi stormed out to the parking lot, and a few minutes later we went out after her. She proceeded to scream at us for a good 10 minutes, calling us jack@sses repeated times. At the top of her lungs. Just outside a church where a funeral has taken place. Then she drove off, and a couple weeks later wrote us all letters about what awful people we are.
I could tell stories about her all day long, that's just the most memorable.
And no, at that time she had no dementia, alzheimer's, etc. She was in perfect health.