Most Helpful Girl
Here's what you need to do; stop contacting her as often as you do.
This girl is playing games, now you have to decide whether you are going to play this game or are you going to put your foot down because it's hurting you?
This girl sounds pretty flakey to me, I wouldn't give her another chance if I was you. But this is your friend and I think you probably like her a lot. If you feel that this is something you really want to pursue, then you should.
But definitely put a limit on how much you are going to give in. If she is seeing this other guy you may have to back off. Maybe they had something going on before you started making your moves?
These kinds of things happen all the time and she might just like this other guy more. I know that hurts but you never know. But if she keeps asking you to call her back, yet she won't answer the phone, that is a bad sign.
If a girl is interested in you she hates to miss your call. And if she does she calls you back as soon as possible because she is excited to talk to you and find out what's up. Even if you just want to say hey.