I obviously posted too late on this thread, but to answer your question they do that to play games and to be attention whores. I had that happen to me, and let me tell you, it's never good. Stay away from those girls, seriously. They are into games and it's not good. They need to grow the **** up.
I will do my best to reply with an educated, humble and honest answer. Ultimately, it is up to you whether you want to listen to my advice or ignore it completely. Sometimes, my advice may be wrong; occasionally, it will be right. Regardless, I want to do my best to give people answers they are seeking.