Help me read this girl!!!!!?

so i met this girl not long ago. we are in different grades, so we dont have any cl together. the only time we see each other is in the hallway, but sometimes she ignores my presence by avoding eye contact even tho she knows that i am RIGHT THERE. however, almost every night, she ims me to talk, sometimes for hours, sometimes just to say hi. i asked her to the prom in a cute/romantic way, and she said yes to it. so i doubt shes not interested in me at all. is it because shes nervous around me? shes a pretty outgoing person from my observation tho, cuz shes very loud and talkitive around her friends. so can someone please explain to me what is going on? thx