What to do about this girl from another town?

Hi! I really fancy this girl, whom I hung out with for a couple of days two weeks ago. We ended up making out and stuff and she told me she fancied me from the moment she laid eyes on me. She’s back in her own town now, only an hour away from here. Unfortunately we didn’t really get to say goodbye properly or exchange numbers, but we’re keeping in touch through facebook. It’s always me initiating a chat, and I’m not sure if that means she’s less interested or if she just sits around waiting for me to write. I’m in doubt as to whether I should write a message where I’m telling her how I feel (it might seem weird seeing as we met so briefly), or just stay chill until some opportunity arrives to meet up again. Whatever I do I’m afraid I might screw it up. Advice anyone? :)