What if my mother-in-law speaks ill of me outside, and I am amiable at home, but I never mention her to outsiders?

First of all, you have to make sure that your mother-in-law really speaks ill of you outside. Do you mind if someone comes to tell you? I've heard of it. If you mind, ask your mother-in-law face to face, don't hold it in your heart. I'm afraid there will be some misunderstanding.

Secondly, the object that a mother-in-law can speak ill of is probably the kind of person who is a mother-in-law. Relax snacks. If none of what she said exists, you don't have to take her seriously. Do what you have to do and ignore the rest.