She was this year's Pop Idol/American Idol (= Star Academie in France) winner in France
Yep Nerea is right, she won the French version of the show American Idol, called here 'Star Academy' (with a 'y', Nerea, hehe!).
Actually, she won the 2nd season.
And yeah, it was me who made a rip of the video. It's actually a pretty nice version of ATFM. Nolwenn has quite a great voice but French producers made her sing crappy stuff...
She sang with Nessa because Nessa was a guest on the show and the contestants were able to choose who they would do a duet with and Nolwenn chose Nessa.