Divorce on the ground of adultery wife having extramarital affair

I came to know that my wife has been in extramarital affair when I checked her phone I found out she hasbeen sending sexual messages to a guy however she denies the fact and says that she was just chatting and did not have any physical relationship but messages say something else and my in-laws are supporting her inspite of this fact and asking me to prove her I'll character. Please tell me what should I do they just denied to take her when I wanted to file a divorce and she is still in my house I have a 12 year son as well and its been 15 years I am being married I am Hindu please advise.