Consulation about sister in law threaten to family

Dear sir my sister in law age near about 29 or 30 has frnakly say crake mind,she dont have sense u can say,every week she always threaten mybfamily to do something wrong with her and complain against us for tortureing her,she abuse every member of family even mother and father,also husbnd,that if husbnd i mean brother told him against doing what she is,she will also complain against him,we were so happy family,but after coming her in my family ,it gone worst condition.every neighbour knows about her nature,her mind is out of order,and always harm herself by doing something like knife use in hand,beaten herself and told i will complain that family is beating me and her family also support doing this,they also threaten us to complain,actully she dont have now father in accident she losses her,and now no one in her family to support her family,so they want nuclear and make my brother as gharjamai,nd support them doing their bussiness and all,but my brother dont want do this,what should we do pls suggest us,bcz she always therten to harm herself and complaint against us,pls suggest all.