A teenaged girl who closely follows or adheres to the trends and preoccupations typical of adolescence, especially as defined or directed by popular culture. The pop-idol's concerts always draw tens of thousands of teenyboppers.You're nearly 30, Janet, but you still act like some airheaded teenybopper.
teenybopper
(ˈtinibɑpɚ)
n. a young teenager, usually a girl. The teenyboppers moved around the mall in droves, not buying and not causing any trouble, just being available for anyone who wanted to see them.