Dear Concerned,
Please note and choose to do the below.
A. As your sister is dependent on her husband and presently staying in her matrimonial house - PLEASE NOTE that any any cost she should not leave her matrimonial house - also note that her husband CANNOT throw her out of the house. SHE has legal right to stay in her matrimonial house and hence no one can through her out.
B. This is a case of Domestic Violence and your sister should contact a local lawyer and file a case of domestic violence in the court concerned, and seek for interim maintenance and residence orders.
C. If she stays out of the husband's / matrimonial house she can claim maintenance - when she is staying within the house then too she can ask for expenses for herself and children.
D. Whenever your sister is abused by her husband next ASK her to call the police and this will help her for her position in her matrimonial house.
DO NOT STAY QUITE FOR THE HARASSMENT FACED - ASK her to raise her voice. Call 100 , STAY on their head in the same house and file Domestic Violence against them .
Best of Luck. Stay Blessed.