How can I get this GIRL to LIKE ME!?

I've had a couple girlfriends in the past but i met this girl several months back. I'm a sopre and she's a senior i like her personality more than her looks that's why she is so different than other girls. So we've been friends fro a while, her snuggling with me in a blanket at the park, hugging me, us flirting (occasionally). I really like her, but recently she has been kind of ignoring me, not saying hi to me at school, walking past looks at me and keeps on walking without greeting me or anything. I talked to her on facebook and she seemed more enthusiastic, but now she is kind of acting a little down towards me. HELP PLZ!