Hard to remember what would have impressed me as an 18yr old. How come dinner at your place is a no-go? Don't want to hang out at your place or just not dinner? Since she likes dancing, you could do a little dancing at home. A couple candles and some music she likes is a pretty easy thing to do.
Or head out somewhere, put some good music in your car, get out and look at the sky if it's sort of clear, and do some dancing. Seems kind of corny, but lots of girls like that sort of thing.
Alternately, what about a night time walk by the river, or even a little night time hike if she's daring? One of the most awesome Valentine's dates I went on was a pretty short little night hike, with a guy I had only been on a few dates with prior to that. We sat at the top and talked for quite some time. The weather was relatively crappy but it was fun, and very different.
Low key, fun, and not completely run of the mill is always nice. Hope it goes well! :)
PS no need for pics of the girl, I'm not a guy LOL