Violence from daughter in law

Hello, My brother got married in December, 2012. My mother lives in school campus as she is a teacher but she occasionally go home and I lives in another city as I am doing job. There are 3 permanent persons i.e. my brother, his wife and father. My father is addicted of drink. My brother's wife is very polite in front of my father and brother. She always react very calmly in front of my father but she behaves very bad to me and my mother. My mother come ones in a month to home. Whenever she comes at home, she always cry because my brother's wife always mentally harras her and sometimes physically too. My mother is a patient of diabetes, blood pressure and Asthma. My mother is of 52 years and my father is of 53 years. we are sure that she will do fake complaints against my mother and may be against me because she hates me and my mother but just because of property she behaves good in front of my father. We are very afraid of complaint. We only want prevention from her fake complaints as her bad behaviour and increases day by day. Please suggest us is there any law of prevention too? Without knowing every one.