Dear All Advisor,
My sister has been married for two year(2016). but 2 month after the marriage, sister's in-laws had started harashment. like (They lived in the same room all day and did not let their room go. And if by mistake accidentally went into his room he would scold her. And speak bad about the girl's parents.And always used to torch the girl.
This is the family matter , try to resolve matter with senior person of the family and as a brother don't interfere too much because it is not good for your sister marriage life .
legally your sister can put cases but I don't think it is required at this time . In marriage up and down is common .so be calm and try to resolve matter in silent way .