I'm picturing something between this (without the top or back):
strawberry shortcake http://www.etsy.com/listing/56894148...u-costume-tutu
Tutu Ruffle Apron http://www.thehobbymommy.com/2009/12...etplus-so.html
But my guess is she's thinking something along the lines of the bottom of a French Maid costume, but hopefully longer (and not the "naughty" Halloween variety).
I think it could be really pretty if it's not too full or flouncy and you find the right fabric for the apron part.