Husband harrasing wife

My elder sister got married this feb. We had a grand wedding. We've spent like a fortune on this marriage. My brother in law used to work in a pvt bank. He was unemployed for 3 months after marriage. The again he joined in another bank around 2 months back. Everything was fine until last two months.Suddenly he started to behave differently. He started what she called as 'mental harassment'. He is constantly forcing not to speak to my mother. Not to answer calls from our family. He keeps saying that he expected more from our family but he is disappointed with us. He asks her to get a job, and he doesn't want to work and start some share trading business. He says he is way more handsome than what she deserves. Her in mother-in-law constantly says that she should ask my parents for TV, Bike, etc. They was never a situation like forcing her or physical abuse. But constant mental harassment. My sister says she cries almost every night. She says he also verbally abuses our family. My father is kind of totally attached to my sis. My father thinks fulfilling all those demands will keep her happy. Theirs is a joint family. The wife of my bother in law's brother is also treated like a maid to entire family. My sis is just 25. What should I do? In case of proceeding legally, what action can we expect? I want the best possible answers.