Harrasment by wife

Dear All, I am married since last 4 yrs. i am living with my old parents, wife and 3 yrs old son. We have been facing harrasment from my wife since last 4 years. My wife is very aggressive in her nature, she gets hyper with every small things in our daily life. Whnever there is any small mistake done by mother, she keeps on yelling, shouting to my old mother. She intermittenlty threatns us that she will do sucide if we do not listen to her. She is not helping my mother in daily house work like cooking, etc. Instead she keep on shouting on mother. My parents are quite old and they never fight with her verbally. From last 4 yrs i have been keeping calm but nowdays its become really difficult to handle such situations. We have even informed this things to her parents, elder sister but they are saying these things are norml and happen in evey house and trying to ignore our complaints. i have already told her to go back to her house but she denies for it. From all above, I want to get seperated as it has become unbearable to me and my parents to manage her in our house. We are also worried for future of our 3 yrs son. Dear All, pls suggest a way out to get seperated.