Wow. I'm gone for a weekend and look what I miss. Luckily, we have an extra week to get him prepared now.
I think you need to look at the specifics of the situation a little closer. She's 23. That means one of a couple of things.
1.Is she nerdy? Maybe she's a virgin also. If so, she either really wants it also, or she's holding out for the "right guy". If she's holding out, it's gonna take longer than a weekend but things will work themselves out. If she's just trying to knock her first boot as well, add booze and enjoy.
2. If you know she's "experienced", then the question is how experienced? By 23, most girls have had multiple partners. They've also lived the bar scene where they've met plenty of guys just looking to get laid. Sometimes they just want to get laid too...and sometimes one night stands are a total turn-off. Just hope you get her in the right mood. Chances are, if you're a 20 yr old virgin, you're not the type to stir her "I wanna be dirty" rumblings. Forget about smooth moves and saying witty things. At 23, she's seen all that bullshit. Just be yourself. The harder you "try" to get in the pants of a 23 yr old girl, the more she'll be turned off.
3. Alcohol. It sounds like you two haven't done any "fooling around" yet. If that's the case, she's not going to screw the first time you make out...unless she's wasted. And that's still a maybe. And she'll need to be a slut. She may be thinking she'd like to screw, but if she's sober her conscience will override her hormones.
4. The virgin factor. A lot of girls have never bagged a virgin (unless it was that high school "first for both of us" thing). At 23 she probably thinks there are no virgin males over the age of 16. She may like the idea of showing you the ropes. It could help your chances. But it could hurt your chances. She may think it's sad, or wonder what's wrong with you. That's where you have to use your instincts. If she appears to really like you, and the conversation or action turns toward gettin busy, you might let her know that you're a cherry. If you're not sure if she's into you, don't tell her yet.
Seriously, forget about doing it on the first night/weekend. If it was some girl you picked up at the bar that night it would be one thing, but this isn't a good "one night stand" scenario. Add your lack of experience and your chances are about zero of making it happen in one day. Just work on laying the ground work. If you guys have never kissed, just work on some kissing, maybe some heavy making out with a little bit of roman hands. If you have already made out with her before, it's time to feel her tits. Maybe get in her pants and bang her, or maybe she'll play a little tug of war. You gotta crawl before you can walk. And it helps to get really good at crawling, to build confidence for that first step.