She might interrogate herself as to why she only wants to date virgins too (if she hasn't already). It might not help any, but if she finds that it's not actually the virginity itself that's important, but what she feels it represents, then she might be able to come up with a less-intrusive question/alternate strategy for dealing with the issue.
For example, if she believes a virgin is more likely to be willing to wait until marriage for s3x, she can discuss sexual mores/expectations earlier in a relationship than flat out asking "Are you a virgin?"
If she's concerned about STD's, she can ask that he be tested before they become intimate and/or (if she's young enough) get vaccinated for HPV.
If she's like me (yes, I was the same way when I was younger/single) and it's about her own insecurity and/or a respect thing* she can decide what she needs to feel secure/respected or work on any unreasonable insecurity issues.
If she does all this, and decides they still have to be virgins, I think Aeris' first two paragraphs sum it up.
*You see, I was raised with the stereotype that boys go out and date and have s3x with the "bad girls" until they're ready to get married, and then they start paying attention to the "good girls." I wasn't having any of that, and decided that if guys (in general) expected me to wait for them, then they'd darn well better respect me enough to wait for me too.