Your wife behavior shows immaturity. Is your wife really don’t want to understand or you think like that. In most of the cases we forget to think about our behavior. First of all rewind all the incidents which happened and think neutrally. Keep yourself in her place and think. Everything has different aspect. In most cases we think that we are right and other person is wrong. This exercise will help you to identify the wrong thing which is happening from your side.
If you feel that you are right and your wife is wrong then you need to talk to her father and mother. Explained them clearly that these activities are not going to help their daughter and going to spoil her life. Ask your father-in law also that his wife is misleading his daughter. Divorce, separation and breaking relationship are the terms which are easy to pronounce but hard to follow. I have seen lot many people who has spoiled their life.
1) Do Introspection first and try to understand your wife’s point of view.
2) Do corrective steps if you are wrong.
3) Be bold and strong and talk directly to your in-laws.
4) Warn your mother-in law for interfering your personal life.
5) Explain them that all these activities are not going to help their daughter’s life.
Let me know you views of my suggestions.