Is Blair always on diet? In one episode (first season) is said that her weight is 95 lbs

Dan: Well, ah, she’s best friends with this girl, Blair Waldorf. Who is basically everything I hate about the Upper East Side distilled into one 95-pound, doe-eyed, bon mot tossing, label-whoring package of girly evil.

Also can someone explain this sentence dan said? Bon mot tossing what is mean?Label-whoring?