a silly flighty person
"I was very good at being a girl and I'm not quite so good at being a woman. I was good at being quite flighty and dippy and a flibbertigibbet. But I don't feel so convincing as a responsible human being." Actress Emily Mortimer interviewed in The Telegraph, September 19, 2005
About the word:
Flibbertigibbet may have been coined to imitate the sound of idle chatter. The word first appeared in Middle English as flepergebet, and it has enjoyed a number of senses: gossip; chatterer; demon; imp. Shakespeare gave flibbertigibbet its current spelling, but the modern meaning only dates to the end of the 19th century.