Wait, did she even con the Gullwings the first time? They had to know that she wasn't Yuna, since Yuna was part of the mission. She sure had me going, though.

But your point is well taken. She can play the concert diva since, well, she is a diva. Plus she dresses like a Las Vegas showgirl even when not on stage.

Having said that, to introduce that ability and then drop it seems like a wasted oppurtunity.