Seeking legal advice for sister's troubled marriage

My sister got married about 6 months ago and marriage isn't going well. The reason being her in-laws (Mostly guy's mother, elder sister and younger sister) keep harassing my sister. Guy himself is alright but he doesn't intervene to stop his family from harassing my sister. Instead he keeps telling her to adjust. Some examples of harassment - 1) They give her too much work to do all day long and don't let her rest. 2) They keep taunting my parents and me in front of my sister and swear all the time. 3) They have placed too many restrictions on my sister and don't let her leave the house or let her even wear clothing of her choice. 4) They have told their son multiple times to send my sister back. This goes on day and night. 5) They even took her jewelry forcefully and don't let her wear it. 6) They even locked her in her room couple of times. These are just some of the examples. My sister lost about 15+ kg in 2 months and stays stressed all the time. Guy himself doesn't bother my sister - but he is too coward to stand up for my sister. He even told my sister with in 2 months of marriage that he can't take her responsibility for her and she should find a job to handle her own expenses (Seriously, gone are days when men used to be real men and take responsibility). The root cause of problem is guy's Mother and elder sister. Guy's elder sister is married but she has troubled marriage and doesn't live in her in-law's place. She wants his brother to take care of her and wants to end his marriage with my sister. We have brought our sister back from that hell hole and even got her jewelry back. I am looking for legal advice to get my sister out of this trouble. I don't want to get into a long legal fight them that can go on for years. I would like to end this soon and teach them a lesson as well for ruining a girl's life like this and wasting our time and money. Any advice is appreciated.