adultery before 2018

No criminal case against her friend under IPC-497 will  be valid

if you were married and she was having the status of your wife in 2016)/2017 and the person who had s*x with your wife knew this fact that the woman was married then this is a crime against you and you can file a complaint in the court directly against your wife's friend under section 497 ipc for adultery.Here you will be considered victim by the court.

thanks Harsh