The best way to deal with your mother-in-law is to get away and stay separately, if you can. Usually, being far from her could bring peace to you, make you happier, and disallow any of her interventions in your personal life.

I understand if you are not in a situation to do that. It could be that your financial conditions or your personal situation might not allow that. In that case, you can do any or all of the following:

• Talk to her: If you feel that your mother-in-law nags you, asks you impertinent questions, or tries to cause you any trouble, it's best if you can take time and try to talk to her. Make her understand patiently, whatever it is that you want her to understand.
• Use the passive-aggresive approach: If talking doesn't help, go passive-aggressive. Simply put, it means that you can just ignore her, almost as if she doesn't even exist. It usually works like a charm.
• Get your spouse to talk and/or go passive-aggressive: In addition to the above, you might try to convince your spouse by explaining the situation. Get your spouse to talk or convince your spouse to go passive-aggressive too.