How can I prove my innocence according to Islam in a false allegation of an illegal relationship?

I am Asghar and I got married 2 years back and I have a daughter who is one year old now. My wife has applied for Khula (divorce) in local Jamat (Mosque). She has made false allegation that I have illegal relationship with my sister-in-law (brother’s wife); however, she does not have any evidence for this and the Jamat did not ask for any evidence when the discussion happened in Jamat. She has mentioned in her Khula petition that once she saw me along with my sister-in-law with my sister-in-law’s room in inappropriate manner which completely is false and Allah knows it better. As per Islamic law she should provide 4 evidences for her allegation. She made the false allegation and she confirmed to Jamat that she was there on the time of incident. She lied by being in Mosque which is house of Allah. My question here is, how can I prove or what should I do according to Islam to prove that I am innocent.