Not really. I think it's more that, since one girl finds you attractive (physically, mentally, etc.) to go out with you, then you must not be too crazy or psycho, so they start flirting. Besides, people always want what they can't have.
People feel that thy r only attractive if someone else wants them. This isn't only a female thing. Its a confident boost when someone is in a relationship and or doesn't want you to suddenly want you. People who do this is very insecure and will never be happy without confidence. This post is misleading.
3001259 x10^7 to go!