Is there any way to see if the girl is still a virgin? By looking at her face closely? Or any changes in her?
Well, if the woman in question took a pen and wrote "I'm a virgin!" on her forehead, that might tell you something.
However, otherwise there are not any signs one can look for to determine virginity short of asking the person in question.
Virginity is not really a physical issue so much as it is a cultural construction. Historically (and even today), the concept of virginity is primarily one designed to be used to control women. While in the past people may have believed that the presence of a hymen indicated that a woman was a virgin, we know that's not true. There are women who are born without a hymen. Also, it's normal for one's hymen to wear away during youth and puberty through normal activities. The hymen is not like a "freshness seal" on a coffee can. It's a tiny layer of tissue that partially covers the vaginal opening. It's not a solid barrier, instead the tissue has openings in it already so that vaginal discharge and menstrual fluid can pass through. The passage of menstrual fluids, masturbation, tampon use, and other activities generally slowly wear away the hymen before a woman is ever sexually active. So usually, (unless we're talking about a violent event like rape or a serious genital injury) this is gradual process over time. There are a few women who do have very resilient hymens which do not wear away mostly or completely on their own and may require the attention of a health care provider. There are also cases of women who have engaged in penetrative sexual activities (or even given birth) and still have some residual hymen left. Also, contrary to some people's belief, a virgin is not going to be "tighter" than a woman who has been sexually active. The vagina is designed to relax when a woman is truly aroused and wanting sexual activity. Sex doesn't cause any permanent changes in one's genitals, hips, face or any other body part.
Another issue you may want to consider here is exactly how you're defining "virginity." As we've already established, there isn't really a physical or medical definition of this. It is basically culturally established. So what exactly is a virgin then anyway? Some people may consider themselves virgins if they have engaged in absolutely no sexual contact of any sort with someone else. Other people may call themselves virgins as long as they have not engaged in vaginal intercourse (but may have engaged in other sexual activities which can have STI and pregnancy risks). Individuals who are gay or lesbian may define it in completely different ways. Some people (unfortunately) define it based on whether a hymen is present. But where does that leave women born without one or whose hymen's wear away naturally? And what about men then? They obviously don't have a hymen! So while the term "virgin" is used an awful lot, people are not always talking about the same thing. This is part of why the concept itself is not terribly useful when you get right down to it.
If you're wondering about a person's past, the wisest, most respectful thing to do is going to be to ask them honestly about it. Looking for signs isn't going to do you any good.
You may want to check out the following pages for more information: