Why did she behave like that? (GIRLS)?

Last year (may), I introduced myself to this girl in a nervous/blushing manner, (She knew that I liked her).But never had a chance to talk. I thought she was ignoring me in school, so ignored her on graduation last year. But then i found out that she liked me so i tried to talk and trying to get her forgivness many months but she rejected me(not desperatly). from october to december She was annoyed by me. Then i december i finnally talked to her, even told her that I liked her but she said that she didn't like me. I even mentioned her that i was curious about her many months before i even approached her. Were not even friends. I stopped in December and continued with my own life TODAY At sport day with school, I was in charge over the barbeque then I see her giving me little glances a few times, she doesn't hold them but just gives the little one. While I was focusing making hamburgers then I saw CORNER OF MY EYE, when she is looking at something else, she takes a little glance at me first then turns back to where she was before.She was doing this 2-3 times (not desperatly) when she sat alone around the barbeque. I saw it all with corner of my eye, when I was at the barbeque. When I later was walking around I we both caught eye contacts and we both looked away. NOTICE: >(she sat alone, all of her friends were walking around but she didn't join them)< NEXT DAY THIS HAPPEND She came in from schoolyard, I was sitting with my friends, she walked past me, when I looked up I caught her looking at me, she looked away like nothing happend. Then later on she went back with her friend, she sat across my table (SCHOOLSQUARE). I caught her looking at me, 1-2 times, she even caught me looking once. We gave each other little glances.( not all the time) few minutes gap. Then later on she didn't look at me anymore. Notice: She crossed her arm and looked angry for some reason. Even to her friend.