It looks to me like it's a pleated skirt, with a very wide waistband. I suppose you could make the bow either from the band, or if you want it kind of cinched like hers is, slip a wide strip of fabric between the band/skirt and the top of the band and just tie a bow. You might have to add a lining to get it puffy like that...
I'm no expert, but it doesn't look too difficult to make! I hope you post pictures if you decide to go through with the project.
