What does it mean when a girl tells you she wants to be single and not serious but she calls you daily and tell you she really likes you. we've had sex. please enlighten me?

It means she's messing you around.

She likes you enough for sex, and occasional get togethers, but not enough to actually go out with you.

She'll call you daily to tell you she's into you, so you won't lose intrest, if you do, how will she get her kicks?

She probably likes someone more, and doesn't want anything serious because she is looking to get with that guy, and just wants to fool around with you until he takes notice.