Need advice for my sister.

My sister got married about 13 years ago. Since day 1 her in-laws had very bad behaviour with her as well our family. Whenever we tried visiting her they created dramatic scenes always blaming her for petty issues. My sister’s husband is employed with a PVT company. She gave birth to a son about 11 years old now. Her son is affected with cerebral palsy since birth and majorly handicapped. Dependent for everything to her mother. She also has daughter now 9 years old. Her sister in-law is also staying at her parents place with her husband. As it was whole drama since beginning they started coming to our place always with some or other household issues blaming my sister and all of us. About 5 years back my sisters husband started living in some rented accommodation alone (though he is getting his regular food from his parents) and his parents filed a court case in family court blaming her to harass them and asking court to direct her to leave their home. And as they have good connections they got the orders in their favour as well. Though it was stayed by higher court. Now they have installed cctv cameras at home and they record even the smallest things and have filed multiple times police complaints against my sister. In this whole situation she takes care alone of her children. There is absolutely no support from them. my sister has no thought and she doesn’t want to leave them.