Roxane Mesquida will play Louis' sister on Gossip Girl in the upcoming fifth season of the CW drama. That will put her at odds with our heroine, Blair Waldorf.

Sources confirm to TV Line that the French actress/model is joining the cast as the meddling sibling of Blair’s regal fiance. The season begins September 26.

Short story? She's not happy with the engagement.

Little is known about Mesquida’s character, but her brother’s impending royal wedding is not what she had in mind, and she's hell-bent on sabotaging it.

It's a recurring role, so expect this petulant princess to become a major player in the drama playing out in at least the first half of the coming season.

Thoughts on this character and story arc? Discuss ...

[Photos: WENN.com]

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.