Can You Tell If She's a Virgin?

Yes, look for the hymen.

Why would she hide for the stats of virgin?

Not necessarily. If the hymen is intact then the guy should be able to tell that she is a virgin but if it isn't intact, then unless you tell us we probably won't know.

Why would you want to hide this from him? As a guy, I would like to know; primarily so I could make it as pleasurable a first experience for her as possible. So you don't have experience. You have to start somewhere and, again, as a guy I would be flattered to be the first. Pretending to know sounds a little lame and you will come across as either a liar or lousy in bed or both. Not knowing is fine; and verbalizing your openness to learn is exciting.

Try saying something like, "I'm a virgin and I want you to teach me everything". You're stroking the guy's ego on two fronts; that he is your first and that you believe he can show you a thing or two about sex.

Depends if your hymen is already broken or not. If it is broken, he can't actually tell. If it isn't broken then it will break and you will bleed, so he will know.
That said, if you aren't able to communicate honestly, then you probably really shouldn't be having sex with that person. Also, like has already been said, I think you come off much worse pretending you have experience (it will just look like you are bad in bed) then saying you have no experience and want to learn. I don't think he'll be offended or scared off if you phrase it right. Probably just flattered.

No not really at first glance but if they do have sex then most likely because you bleed. Not a period bleed but just a temporary hour or two bleed but she could easily lie and say she started her period. They probably couldn't tell also if she didn't do any of the work but if she has to do some then it might come clear. It just all depends on the guys experience to. If it was the other way around and the guy was the virgin then it would be very clear. Lol We just know. To answer your 2nd question. If you couldn't tell who cares because most guys are just happy to get off. But if it was a long relationship before sex then yea because that something that should be disclosed so that there is an understanding in the relationship. Plus that's something that should be treasured. But as I said it all depends on the situation.