How to file for a divorce against cruel husband?

Dear Sir/madam, My colleague and I are in love with each other. She is married and I am single. Her husband doesnt love her and never touched her after her first child that too occurred due to family pressure. Every day he and her in laws dont behave well with her and always say she is ugly or her dress is bad or cooking is bad or any other comment and taunts. She is living her life with that man only because of her child who is 6 years old. Her husband no doubt never stop her from spending money and always give money to her for her shopping and other usefulness needs. But she doesnt get the emotional and physical love from him and her in laws which require a woman to live a happy life. She is going through so much of mental depression and stress. I came into her life just 4 years back and are in love past 1 year. she is married for 8 years. Please advise what to do. what to do to file for divorce. I dont think her husband will give mutual consent to divorce. Please advise.