Okay, this situation reminds me of a couple I know from church, whom are my age.
The wife, a friend of mine, went on a retreat with me back in April, and she told me something about her that I'd never known before. She lost her virginity as a teenager. She met her husband while in high school, and when he found out, he was angry (though it happened before they met) and wanted to break up with her. After all, he'd waited and wanted a girl that had done the same. But she made a point to him that is very important for all of us to consider. She told him that God had forgiven her, and so should he. If God can forgive all of the sins we have committed, knowing it was because of us that Jesus was crucified, then who are we to not forgive others for doing things in the past? We ALL make mistakes, and fall short in some areas.
Now, if you want to marry a virgin, have prayed for that, then there's nothing wrong with wanting a future spouse who has also waited. It's what I hope for, so I'm certainly not criticising it.
But to say that this girl is somehow worth less because she made a mistake is hurtful, and is certainly not how God sees her. If you're hurt, imagine how she feels when faced with the knowledge that she gave something very special away, that she cannot get back? Imagine how she feels knowing that she's looked at as worth less or "damaged". It doesn't sound like what she did was something done to hurt you, though you didn't say whether she'd cheated on you or not. That would be a completely different circumstance. If it is something that happened before you began dating, then I hate to be harsh here, but you need to get past it and learn to let go of it, as it is not a choice she made to wound you, and it's not fair to her to hold something she did in her past against her.
Now, if dating and someday marrying a virgin is important to you, then that's great! There is absolutely nothing wrong with setting those standards and holding to them. If it is a desire of your heart, pray to God that He will provide you with a girl who has waited. But if you want to be with this girl, and you really care about her, then you need to realise that God has already forgiven her, and He has a lot more to hold against her on this matter than you do. Ask God to help you forgive her, to see her the way that He sees her, to feel God's love for her, and try to see things from her point of view. And, most importantly, pray for guidance on this situation. She may not be the one you are meant to be with. And, if not, then not only does God have an amazing girl in mind for you, but He also has an amazing guy in mind for this girl who will be willing to put aside her past mistakes and love her for who she is right now.