If she doesn't know about the things she says then she won't know the weight behind the question "Are you a virgin?", then she won't be shocked or even care of it. But because she showed reaction to the question that means she understands it fully. I think the shock comes from the fact she didn't expect sensei to ask her, or maybe this implies that he believes she's a slut and doesn't love him as genuinely as she claims. I'd take that as an insult. Assuming I was chick.