My MIL always interferes whenever I discipline my son. As a result, my son always runs to her whenever I am disciplining him and this has made him defiant. How to tackle this situation?

the best way to tackle this is to talk to your hubby first, and if he doesn't understand, then speak to your MIL directly. i feel that as mothers, we really need to stand up to people and assert ourselves. don't be rude. just be firm and tell her that your son will look at her as a role model, so instead of pampering him all the time, she too should take care to discipline him. try and be smart about the words you choose ;)