It isn't totally clear since the reader is not given the chance to follow Clarisse around through her life except for her interactions with Montag. It is clear that she does not do things her peers are into as she describes them as so vapid and meaningless that it is obvious she doesn't really get along with the in crowd.
She also discusses the fact that her family likes to sit around and talk and discuss things which suggests that perhaps her whole family is somewhat separate from the rest of the society, the one that Guy's wife is so willing to accept and follow.
Clarisse states that all her friends are victims of car crashes or homicides. Clarisse states that she has been deemed "anti-social" because she actually likes to socialize and talk with other people, not crash cars, watch television, or speed. Through indirect/direct characterization Bradbury gives us the picture of a young girl who does not fit into the society she was born, and because all the friends she did have are dead, she is a very lonely young girl.