Urgent Legal Advice Regarding My Sister’s Marital Situation

I am reaching out for urgent legal advice regarding my sister’s marriage, which took place in September of this year. While we initially believed her husband’s family to be kind and understanding, we have encountered serious and distressing issues. A few weeks into the marriage, my sister started facing challenges in adjusting. Her husband, who we noticed was a bit short-tempered before, has exhibited increasingly aggressive and abusive behavior. Recently, the situation escalated to physical abuse: • He threatened to slap my sister if she didn’t comply with his demands and move out of the room. • He held her face so tightly that her jaw began to hurt and left her deeply shaken. • He also grabbed her hand with excessive force, leaving visible marks. • His father later entered their room with a gun and placed it on the table, which terrified my sister even more. • After this incident, her husband went to another room to sleep and again threatened to slap her. Traumatized and scared for her safety, my sister returned to our family home the following day. However, when we approached her husband's family to discuss the matter, they refused to consider a divorce. Her father-in-law was particularly aggressive, stating they would not let the divorce happen under any circumstances. What should I do?