Legal Notice or directly filing Divorce case ?

Hello Lawyers, I am in a dilemma whether to issue legal notice or to file a divorce case to my wife. Our marriage relationship is 3.5 years old. She fought with me and went to her parents house few months ago and we are not staying together from past 5 months.After she going to her parents house , our family and her family together had 1st round of discussion and during that discussion she and her parents clearly told that she will not come back and stay with me again and she took away her clothes.1 week after this discussion my wife called me one day and told let us finish this mutually and legally and she even told me to call her when I am free so that she will get the legal papers ready for mutual divorce. I have call recording of this. After this conversation , we tried to contact my in laws family several times but they haven't responded back till now. Even though she only had told about mutual divorce , but people may have brain washed her stating let guy initiate the divorce process so that they can claim compensation from me. We consulted a lawyer and he asked us whether we are ready to take the girl if she comes back and we said "NO". For this lawyer told let us file a divorce case instead of sending legal notice coz if we send legal notice ,the girl might change her version and agree to come and stay with her husband. I don't want to stay with her again coz of the mental torture she has given me from past 3.5 years.So lawyer advised us to file a divorce case instead of sending legal notice. PS : Since my wife went to her parents house on Oct 6, 2016 , she has not filed any police complaint against me till now. So If I file divorce case now and if she gives police complaint now , will it stand ? Also kindly let me know which is the better option - filing divorce case or issuing legal notice ? any suggestions would be much appreciated.