Help regarding the filing of case against my sister's husband

Sir my sister is married for almost 2 years it was love marriage. From the next day of the marriage the mother in law of my sister started taunting about each things like ' what have your parents given us in the marriage'. My sister earlier was working as a architect under reputed firm but after marriage she left the work but when she requires money even for some small things they does'nt gives but instead of this say ask from your husband. Her husband does not do any work as their family have the quaters which are rented to the labour worker so they do need to do any work her husband only take 10000 from the parents as his pocket money for the month but after marriage that also got reduced to 6000 only now you can see how she can ask any money from her husband. So she decided to work again. Then new thing appear that in laws started to say thatyou will not keep your salary with you give that to us. She refused to that this was about 6 months after the marriage then she called us and we went there and talked about it and decision was made that they will not ask for any money. After somedays the new thing come that you have not bring any bed from your house so we cannot have baby these are our so called 'rivazz' we talked to them that before marriage why you have not told about these 'rivazz'. Then they said ok we will not ask again about this . My father is a retd. govt officer he retired on last year september after that they started to trouble her more n more as they knew that on retiring my father has got his saving about some lacs. She started to telll us about that then we told her that you married him with your wish we cant do anything about this. Then after some time they started to threating her like saying i will throw you from the terrace and if you will do anything against us your brother will suffer etc etc. Her father in law used to scold her daily and threaten her if you will go to court the lawyer will destroy your charcter by asking dirty question as he work as the brokers of the clients whose cases are pending from many years and says he has many links and he also used to give false witness in many cases my sister has even listen him talking some divorce case clinets that dont worry we will say in the court that the girl is having affair with someone else. After this my got frightend and kept silent and continues her routine. Then on 29 april of this year my sister and his husband gome for the dinner everything was fine untill they reached home as they reached home her husband started to force her that give your all salary to my mother but my sister refused so he started to abuse her and scold her and told her get lost from my home and i will do second marriage etc etc. She got frightend and called us and we went there and bring her back to our house. After 3 days her husband came to our house that he is sorry he will not do anything like this again. We told him that okay but we will not send our sister back to that house as they beat her torture her mentally and even the small brother of her husband also abuse her mentally. So he said ok he will get seperted we said ok. After that they started searching for the rented portion and final it but bef9re shifting my sister was having her part time degree exams so she went to chandigarh and her husband only gone there with her and comeback. When after 10 days she came back her husband started saying that he cannot get seperate you have to come to his home only but dont agreed. We told him that if you want her to go to your home you have to give us in writing that your parents and you will not scold and demand anything again from her he said ok and said need some time for this after 2 days his father called us and said we will not give anything in writing. So we said we will not send our daughter there if they want then we will call some of our relatives and you call your relatives and in front of them you give gurantee then only we will send our daughter back but they refused to that also. So hang up the call. After somedays her husband came and said he will get seperated but hus parents will not give any money or support and he does not have money to rent the house and need 3-4 lacs for furniture and extra items for rented house.so we told him that if he want we will give him the money or he can get the furnished rented portion and we wi pay the first 3-4 months rent after you both have to manage as my sister earn almost 50000 in month he said ok i will tell you in 2 days but after he starter to kill time like my parents are not well or i cant leave them etc and then from last 4 days he not answering our call. So my nana ji went thier and talk with them and they said that they will not seperate their son will not allowmy sister in this house. So i want advice that how should we procedd further and what kind of case we can file against them as we will not allow them to roam free