Ask Evie: My Sister-In-Law Publicly Criticizes My Brother. How Can I Make Her Stop?

READER’S QUESTION: "My sister-in-law berates my older brother in front of family, friends, and strangers. She openly insults and criticizes him for things he does or doesn’t do or habits he has. I don’t believe anyone deserves to be treated that way. How can I get her to stop without feeling like I am trying to influence their marital relationship in a way that is not appropriate? I have told her she has issues and needs to learn how to regulate her emotions. I have had a similar problem with friends who openly berate or criticize their boyfriends in front of me while at a dinner, for example.