Poor marriage relationship

Married for 15 years with one 14 years old girl child living in Kadubeesanahalli, Bangalore. Having issues, differences, fights and stayed disconnected during the marriage period. Some are my faults and some ore hers as well. The major issues are towards opposite sex interactions and observations. I am held responsible for the poor relationship. She had past relationship before marriage who married before her and she continues to remain in touch with him. He is married and had son. My wife always chose to go to him when we have bad phase of relationship or will just do chit-chat when our relationship is good. I have requested her that I can't accept this connection and I somehow always felt that she can't get away from him. He equally is always more than 100% towards my wife. Recent fights have resulted in major cut-off between us and she said that we are no more husband-wife and she chose to do whatever she wants. Now, they are very well connected back. I have therefore asked her if we can divorce and mutually close this relationship. But she refuses for my daughter's future, the trauma and probably she wants to live like this till my daughter turns 25 and then she will move out. I don't agree to this condition. I see that she has marital affair and I can't do much in it.