Losing your virginity isn't the humongous deal a lot of people try to make you think. First time is often, messy, uncomfortable, unpleasurable, and emotionally awkward.
When I lost mine I was like, "That's it? This is the huge big-bad everyone talks about?" (although I was raised Southern Baptist in the middle of California, so maybe that was just the local culture) I felt a little hurt at first too, shocked at what I'd done (again, Baptist guilt), scared about the difference (which there wasn't, other than a new option in relationships), but after a while I got over it and found myself to be relieved to be rid of such a silly contrivance. Virginity is damaging to both men and women, not as a state of being but rather as a concept. Sex is natural and bound to happen, no one needs to feel bad about it (as long as it's consensual/legal, with legal being things that are banned for a reason like rape, not stupidity like anal sex).
As to the girl I'm afraid all you can do is attempt to maybe have a mutual chat about each others feelings and the fact that having sex doesn't bind either of you to anything just to wipe the slate clean and part ways amicably. I wouldn't push the matter, though. If she wants to just leave things there and pretend it didn't happen, fine, you could send her an email with your thoughts for your own closure.
Having sex with someone won't make them stay with you and it's not a good mindset to be in. On the positive side now you'll be more able to share a sexual relationship with anyone you may be involved with romantically down the line, and while they might not be your first you'll be more comfortable with it and yourself when it does happen.
(I feel I need to add a slight disclaimer since this is such a personal subject, but this is based off my experience with losing my virginity and the facts that I was raised HYPER conservatively and that I worked up to it as a "I want this person to be my first even if it doesn't work out." Also, for background purposes, I'm a psych major alumnus and someone with a rather progressive view of sex/sexuality and the social stigmas thereof. Just wanted to lay that out there so people don't think I'm talking out of my ass, lol.)