Why does she keep rejecting me?

So, this is a complicated situation that I definitely cannot explain in one Sodahead question -- but I will give a quick summary. I'm 19 and for about 8 years I have known this girl (so we're childhood friends) and this week, since Thursday until Monday, my family is staying at her family's house for Memorial Day as my mom and her grandmother have been friends since their teens -- also my uncle is married to that same grandmother -- (I said it was complicated) -- anyway, I've always flirted with this girl, even when we were both way to long to be flirting and she has always flirted back, sometimes more aggressively like jumping into my arms and laying on me. Two days ago we were in the same room and playing Call of Duty and I looked her, she started smiling, we flirted quite a lot; and so I asked her if I could kiss her and she literally said "no, just no" in a tone that reflected repulsion. I was so flabbergasted that I could say anything, I just sat back had a sip of water and got on my laptop. I could sleep that night because I was so shocked, embarrassed, and humiliated. The next day I completely ignored her and she seemed visibly depressed as if she wanted me to give her the same attention as I did before. But I had it in my mind that I would play a sort-of mind game of my own. That night I was lying down and she came in to play Call of Duty again. She laid sat and laid in the bed with me though I ignored her aside from getting as close as I could to her. She again, was quite flirty, and when she beat the game she sat there looking depressed and as if she was crying. She seemed to reluctantly leave. Then this morning she was more flirty than she has ever been before. She kept coming in the room standing there watching me play video games, smiling. And told my little cousin to leave the room because he is a loud mouth little fuck, and she too seemed eager to get him out of the room. When he finally left, I told her to sit next to me, she did, I was sure that she wanted to kiss -- we sat there smiling at each-other and so I asked her; she again said no. What the fuck is she doing to me?