Here is another video from one of the Marsielle shows. From the applause when she is introduced and after the performance it seems like Alizée is still a big hit with the spectators. Perhaps that's why she was asked to return for a third season.
Well, that and I've heard some chatter this week.... It's possible that they invited Alizée because the winner this season isn't able to participate much. Of course she wasn't in competition this first show but since the one woman had to back out due to an injury, well, you never know. It's all about selling tickets and the producers know that Alizée pleases the dance fans.