How To Save A Marriage From Divorce Due To Inlaws Issues

My daughter got married before 1.5 yrs,she&her husband got separated after 4 months of marriage. Starting from Day1 after marriage, her in laws kept abusing her verbally for petty things such as not wearing a saree at home, staying in a room after coming from the office, using a machine to wash clothes. Her FIL once tried to slap her, her husband stopped him&took her to her office since he cannot control his father. But that day eve, he supported his father&scolded her badly. The next day, he apologised to her. After a lot of such issues, we suggested letting them live separately as a nuclear family so that they can understand each other well. But her husband stopped communicating with her after that.l contacted him many times but he keeps saying my daughter must learn to accommodate to live with them. From their end, they have not taken any step to unite them. We don't want to go for divorce, since we believe that without inlaws influence, they can have good life. Please advise how to proceed with this legally.