My mother-in-law always tells me that this is not good for my sister-in-law. On the surface, I don't care. Actually, I'm bored with my stomach. It can be said that I am tired of both of them.

You have realized that this is bothering you, so learn to let go:

We don't like some behaviors of others, so we can say "no". First of all, I think you are very sensible. Although you are annoyed with them, you still don't want to offend others. You can say like a daughter and mother coquetry: Well, let * * (your lover's brother is your sister-in-law's husband) talk about her. Don't be angry. It's not good to be angry. The advantage of saying this is that it is not clear who will tell elder sister-in-law, and your tone can be understood by the old man as letting her talk. She'll understand that you don't want to get involved.

We can make ourselves happy when we can't stop others' behavior. Maybe your mother-in-law will still complain to you, so what you have to do is not to make yourself unhappy, but to listen, and the content makes you sick. If you torture yourself with it again, it will be cruel to yourself.