How to fight against an evil mother-in-law?

Throw at each other, everyone else is a joke.

If you quarrel with your mother-in-law, others will lose something, and they will be happy to embellish it for you. You'd better play, then they will be happy! Those people are idle people who are willing to tell the story of Zhang's parents and Li's family.

In your present situation, your mother-in-law occasionally speaks ill of you when chatting → a nosy person embellishes it → you get angry when you hear it → her mother-in-law is even worse → her mother-in-law often complains to others → more bad words are passed on to you → you become more and more angry and eventually become a bad daughter-in-law in a nosy population. After you really become a bad daughter-in-law, your husband will go from perfunctory mother → really think you are too much → quarrel with you → you are really isolated, and the next situation can be imagined.

And the elder sister you mentioned, she failed in dealing with the relationship between mother-in-law and daughter-in-law. Do you still exchange experiences with her? There is a selfish side to human nature. If she doesn't live well, subconsciously she won't want people in the same situation to live well, so as to seek comfort in the same boat. If you solve your problem, she will lose your "friend" who can vent, and she will fail even more. Think about the advice she gave you. Is it developing in a good direction?

My suggestion is to exchange experiences with those whose families are harmonious. Those people are really useful mentors for you.