hi thanks for using healthcare magic There is no method to find out whether a person have had sex before. In case of female, if a female is virgin, in that case her hymen would be intact which could be one way to detect about past sexual experience, but hymen could get rupture in multiple ways like masturbation, running, cycling etc. In ur friend case, even after multiple sexual exposure, her husband would not get it. dont worry, tell her just remain faithful with her husband, that is more important. thanks