She rejected me to prom, how should i act around her now?

2 weeks ago (on friday) i left a flower on this girl's doorstep asking her to prom. later when i called her or texted her she didnt answer. i saw her at my friend's kickback the next day and she ignored me.. so i know its a no.. i haven't seen her since then becuz of spring break and when school starts, im gonna see her everyday since we kick it together and have cles.. part of me says "**** that , she didn't even have the guts to give me an honest answer" the other part says "act cool and let her see that it doesn't bother you".. but i dont know which it should be?? it really annoys me that she just avoided me. how should i be when i see her on monday?