Is it okay to tell my mother in law how to cook meat
why do you want to tell your mother in law how to cook meat?
There's is a problem with her way of cooking meat. It tastes awful.
If you have more knowledge or experience about cooking you should share it with your mother in law. At the same time you shouldn't mock her cooking style.
I don't need your attitude.
I'm only saying you should be careful to avoid coming across as disrespectful when helping her improve her cooking. She may think you're just criticizing her otherwise. You don't want her carrying a silly grudge against you.