text: how can a girl becomes a women? how can u tell if a girl is in fact a women , give me an example if it's possible. some girls are born opened how can u tell without having sex that u r naturally open wha? biologically a girl becomes a woman when she starts menstrating. if you are talking about the hymen, it usually breaks when she has sex for the first time but not necessarily, mine did from riding horses. you may be able to tell if she "still a girl" if she's really tight and it hurts her when you penetrate, but probably not.