Divorce (wife threatening me)

My wife threatening with her boyfriend (who is plooice too) saying she will put mulitple cases on me to get divorce. We both were leading happy life for 8 years , we have 3 year old daughter. Recently she got connected with her boyfriend , Thinking my daughter future i was quite for some time. Then i started questioning her coming home late , lying to me about office work. Then i informed to her family ( mother. , brother , sister and her brother in law (sister husband). Her family is in support of me as i was taken care of my wife and their family till now in very good and gentle manner and her family is ready to do any kind of support to me as they know me very and my gentleness. But my wife threatening me always and says she will complain on me . I got scared every time. Now my wife may go for divorce with multiple cases on me. Now what should i do ? Shall i file divorce before she goes ? if go first for divorce any advantage or disadvantages to me ? What if she goes first ?