Is my wife having an affair based on her comment?

My wife had always believe that if you don't see personally if any one is having affair then it's not good to blame, I agree, once I was helping my friend for he needed some advise when he had car accident and his wife as handling the claim process because my friend was working long hours. i had to visit with my friend's wife to the car garage couple of times in broad day light, once she told me I am more concerned about other's wives and she need to talk to my friend to keep an eye based on this I told her you have been talking about your BIL a lot and who is helping your family $$, are you having affair with him and she said no but also said "IF LYING PROTECTS ANY ONE THEN IT DOES NOT MATTER", Also my wife married her BIL to migrate to USA. I told her my friends wife treats me like her brother and after the car accident claim was settled we hardly talk to each other while she does not fail to mention about her BIL almost daily