Whys she acting so weird around me? please help?

Ok so heres the story. There's this girl at varsity that I like. We sit next to one another in most cles. She's really shy and so it took us a while to get talking and stuff. So the other day we where really getting along well. So after the lecture i asked her if she wanted to a see i movie or something the next day. So she said she would let me know the next day. The next day I got a message from her late in the afternoon saying that she was feeling sick and wouldn't be able to make it. Now she's acting all weird and stuff around me and its so awkward. What can i do to try and fix this?