How "datelike" would you want your prom date to be?

she is acting different around you because she knows (or is at least guessing) that you like her as more than a friend. Its making her feel weird because she most likely has no interest in you. Do not go to prom thinking that you are her boyfriend. You guys are going as friends and unless she tells you otherwise, act like her friend. Don't start holding her hand and try to kiss her. You can buy her a corsage but because you are her friend not because you want to act like her bf. If she shows some interest in you at prom, that's great, but if she acts like your friend, just accept it.