Why is she playing games?...?

Do girls generally play games with someone (ie: not always returing phone calls but then sending random text messages, not always emailing back...etc, etc) because they like the other person, want the other person to like them more or just do it to give themselves an ego boost? I am talking with this girl who I get along with well, but is being distant with random games she is playing. She is a cool girl, but I don't want to mess things up by showing her I am frustrated by her being a bit distant. I am all about respecting her space, but it's tough sometimes when I am not sure what she is thinking. There could be many reasons for this...dating someone else, not ready to date, not that interested, etc. I think this can be turned around in due time, but what is usually the best approach?Why is she playing games?...?
Dude, if she was into you she wouldn't be playing games with you. She would return your calls pretty quickly. You would be better off finding someone else to give your attention to. Once she sees you are kind of laying off her if she is interested you will know pretty quick. I hate to say this but if I ignore girls I think are interested in me (but they are showing these signs you talk about) that turns them on and they come chasing after me. If not, then they weren't really interested in the first place. Go after someone else. Why is she playing games?...?
I think you should just move on.