Margo Roth Spiegelman is a very insecure person in her secret life. Nobody knew who Margo really was behind that chestnut hair, those blue eyes and her dark red nail polish. She was very popular which was good, but inside she didn't enjoy being with the popular group. She would rather hang out with Quentin, Ben, Lacey, and Radar.
Margo is an unusual girl and is more of a mystery than people would expect her to be. In the movie, Margo is portrayed to be rather selfish and a bad girl, but in the book she is a misunderstood individual by herself and others. She's a one in a million type of friend who is just interesting. No one knows her true personality because every person that's ever looked at her sees what they want to see, not who she really is. She likes to get revenge in a quiet, sneaky sort of way as proven in the first part of the book.
Margo moved into Quentin's neighborhood when they were both children