My mother-in-law spoke ill of my sister-in-law in front of me yesterday. I don't know how to answer her. My mother-in-law said my sister-in-law made her angry.

Mother-in-law can tell you the truth and prove that she trusts you and knows that you won't gossip. Her original intention may be to talk, just to vent. Just listen, don't tell her that my sister-in-law is not. When she finishes, you should persuade your mother-in-law not to be angry with her sister-in-law. As a family, everyone makes mistakes, so how can she obey her wishes? I told you, just say where you are. Don't worry about it, and don't let your sister-in-law know. Otherwise, if you get angry, you will lose face.