Man, you have been friend-zoned a long time ago... facebook is a good way to exchange a few messages and make plans for meeting in REAL LIFE. When the "relationship" takes place on facebook, you have been friend-zoned... because you cannot fuck a girl on facebook, you need to meet her in real life...
My advice, ask her to meet you for drinks, if she says yes, escalate physically, if she says no, freeze her out for a week or two, then invite her again. Cut the facebook messaging and push for a real interaction... Good luck!