After all she's her rival for the affections of her boyfriend Chuck Bass.
But when Leighton Meester - the starlet who plays the New York princess - caught up with actress Clemence Poesy at Paris haute coutue, they clearly appeared to have a cordial relationship.
As was fitting given their position in the front row at Karl Lagerfeld's breathtaking show for Chanel, the pair were looking chic.
Leighton was on bombshell form in a skin-tight leather dress embellished with faux gems around the neckline and Clemence wore a sassy dove grey shift.
In recent days, the gilded young Gossip Girl cast has taken over the French capital as they shoot scenes for series four.
Leighton's friend and co-star Blake Lively was mobbed as she attended fashion week.
Sshe rubbed shoulders with the likes of designer Christian Louboutin, Gwyneth Paltrow and Elizabeth Hurley at a party thrown by couturier Valentino.
At the end of season three, Blair was seen deciding to go on a heartbreak holiday to Paris after ending her on-off relationship with handsome aristocrat Chuck – actor Ed Westwick - once and for all.
Ed's presence clears up one mystery for viewers. His character was mugged and shot in last season's cliff-hanger.
He filmed some of this week's scenes with a walking stick, playing the part of a convalescing man.