For advice regarding hindu marriage act case

Sir, I am kulbir singh from chandigarh and i take a advice from you regarding issue of Hindu Marriage act. The matter is that, my sister married in 2017 with a man who is doing job as a lecturer in a collage on contract basis. They were four people in their family one is father-in-law, mother-in-law, a sister and my sister's husband. the sister of my brother-in-law was get married before his marriage. but she have no child at the time of my sister's marriage. she is a doctor's helper in near hospital by profesion she did'nt like that a baby come in her brother's house before her. when she found my sister got pregnent that time she started quarrel with her. Some days before they all familty members were shouting at her and they beat her also. then her father-in-law call us for tell my sister's bade things.When we reached at their house, they packed her bag for her father's house. and they were told us that they will surely solve all this matter within some days. but now one and half year is spent and my sister is at her father's house. her father-in-law was retired from police department as a inspector. he register a case for divorce in session court behalf of his son. and he is using his all approaches for make this case in his favour. we have writen judgments of family welfare committee that all blems from the petitioner's side is wrong. so please behalf of this matter give me your valuable advice that what we take next step for make all this matter solve.