Why this girl is playing hard to get?

I Invited this one girl to a Military event. When I called her she told me she needed a few days to think about it, and said she would call me back, because she need a few days to think about it. I did not hear from her so I let a week go by before I took the initiative and called her back. She said she would go with me.

She went to the ball with me. I know this girl, well she is not that shy, but for some reason that night she was shy, and I had to start all of the conversations. I am very confident because I am an officer and that's how officers need to be. My friends told me I should be the first one on the dance floor in front of everyone. I told her that and she told me that she hates when people look at her. ( this is a complete lie because she is a Very attractive girl). She is very insecure about self, and has no confidence at all, she is always hanging around with guys and guys are always hitting on her. Her brother is a good friend of mine and I know her well. Her brother is very out going like me and is not shy.



The event was about 4 hours long and for about 3 hours she did not ask me that many questions. I was beginning to feel she was not into me So i just stop talking to her and just danced with her. With about an hour left she just opened it up and started talking and asking question. When we left I dropped her off at her house and she gave me the biggest hug ever. She told me I was fun person to be around, and we should hang out again. So I called her back the next night, talked to her for about 10 minutes, and she had to go. she said she would call me back the next night, which she never did. 10 days later I had tickets to a pro hockey game I called her to see if she was interested and she said she would call me back, but never did. I sent her a text that night she never responded. Why do girls bother playing around like this. Why won't they call ever. I went out of my way to invite her and call her. I think that she might like me but its hard to tell because she is not calling me back. As of now I throw the towel in and feel I should give her one more call if she says she will call me back but never does I will not talk to her any more. If I do call her back again and she says she will call me but doesn't what should I say to her. It won't bother me If do not hear from her again. It will be her loss not mine.Why this girl is playing hard to get?
If she's too immature to even return a phone call...I would look elsewhere...