Defamation for crime as theaft and other things

My name is mausam thakur and i want some legal advice here. My sister ( cousin ) has habit of having multiple affairs and she stole gold at her own house which belong to her father and gave it directly to her boyfriend. Which she herself told me on watsapp i still hold those chats. Where its proved that she stole it. Then she had affair with a married man who has a kid already. Who isnt even divorced. She was about to run away with him and she told me about it so to save her from this i told in the family about her then my family told her parents and tried to save her from this mistake. But later when her parents confronted her about this she blamed everything on me thats I told her to run away with him and i told her to steal that gold and give to her boyfriend. She sleeps wuth diffrient boys and click nudes herself and give to those boyfriend . I have proved to family that i didnt do it by showing those chats. After few days later as now her boyfriend is threatening her family that he wants to marry her or he will not leave them easily ... one of my relative called me and told me that her family will go to police station to complaint againts that man who is threatening them . My problem here is she first blamed her gold stealing crime on me that i told her do so and now she is also telling everyone that the man she has affair with is my friend and because of me she came in contact with me and i made her do all her dirty work i took her into wrong track. Her family is spreading this lies in whole family and they are trying to put evrything on me and save their daughter. Because of her and her family now i m blamed for everything . In my family my reputation is damaged my whole status is ruined . I want to do something to save myself . And also get my reputation back to how it was. I want to file case on her . But i dont knw how ans which . Please help .