Funny, but an honest question and certainly no less silly than asking if oral sex is really sex.
Yes, is the quick answer, however it depends on a lot of things. And no two women will be exactly the same. But if she claims to be a virgin and DOES NOT bleed at all after first sex..be suspicious of her virginity. But having said that, it isn't as simple as just that, since the hymen can be ruptured from a variety of causes, ergo no bleeding after her "first time". I wonder why you asked this.