Reconnecting with a girl?

[cool dude 456]

So, I went on a trip this summer with a group of people from both my school and a different school over to Europe. There was this one girl from the other school who I met who is smart, pretty, athletic, spunky, hilarious...pretty much everything I like in a girl. We hung out a good amount of the time, and she seemed happy around and talking to me. I liked having her around for conversation, and we started a friendship even though we'd only known each other for a few weeks. Once we got back, I followed her on twitter and she followed me back, which I guess might be a good sign.

I realize now that I miss her deeply. I have strong feelings for her. I'd never really though about it while we were over there, but now I do. I really want to get back in touch with her, but I don't have a number or facebook....

So, here's the question: What do I do? Should I send her a message over twitter? If so what should I say?

Thanks in advance.
Would it be weird if I messaged her? We haven't seen each other in months, but I'd like to see her again; that's why I'm asking this. How do I pull the trigger on this?