Girl's Behavior

Why is she acting like a total biznatch after rejecting me?

It seemed she really like me before hand we talked for a bit and even one of her friends would tell me she likes me. This happened for a period of 3-ish months. I'd also catch her checking me out sometimes. When I asked her whether we could go out. She said no, "She had someone else, didn't see me that way I'm sorry." Typical things girls say. Then sudden, out of no where she'd get close to me, instead of leaving me alone. Like she could've literally sat anywhere in the room but decides to sit beside me. She never talks to me anymore instead acts all fidgety and nervous. Worst of all when she sees me in the distance she'd go up to a boy and talk to them. She'd give me this smirk and look and then dude would look my direction as well. I do not like her anymore what the heck is she doing?

Why is she acting like a total biznatch after rejecting me?
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