Immediately Sister should admit to the hospital and send intimation to the concerned police station. And try for to file a complaint under IPC 498A.
IPC 498a was made to protect a woman from injury to life or limb, or mental harassment to the extent to drive her to suicide. All problems in marital life do not attract 498a, to the extent made clear in this SC judgment too. 498A IPC is a pure criminal offence in which punishment is awarded to the offenders. 498A is a criminal offence that came into existence to combat domestic violence and protect women from dowry harassment
File petition for protection and maintenances from her husband under The Protection of Women from Domestic Violence Act, 2005. The DV Act provides that the aggrieved person may approach not only the Magistrate but also the Civil court, Family court or any other courts and seek relief’s including protection orders, residence orders, monetary reliefs, custody orders, and/or compensation orders. The D.V. Act has been enacted to provide a remedy in Civil Law for protection of women from being victims of domestic violence and to prevent occurrence of domestic violence in the society.
File a petition for divorce on the grounds of mental cruelty and seek permanent alimony.