Mental harassment by in laws

I have been married 13 years now, I have a 9 yr old son. We were staying in a home which my husband and my mother in law built(financially) as my father in law had passed away long back. My husband has a younger married brother who stays with us and a married sister who stays 1 street away from our home. As I was working my mother in law never liked me and always put undue pressure on me on what I should do or don't. I worked from home after my marriage so her constant nagging about household duties of a daughter in law kept on increasing though I always did household chores and also my job from home. Even my younger brother in law and sister in law used to say something to make me feel small and disrespected always. Around 1.5 years back after she had mentally tortured us so much we decided to come in different city and stay on rent. We locked one room in the house that has our personal belongings and all my stuff from marriage. That home is in my husband's, his brother and my mother in law's name. Since we came here she has been continuously pestering us to open the room and now she is saying she will break the lock but that room is the only advantage we have. What should we do. Please suggest.