Do what Soupy does, and go as a guy! I was up until 4am re-doing her 'Kaiba' costume. The 'skirt' I'd put on it before was not long enough around the waist, so I took it off, cut in half, then made a new back panel for it and sewed the two other pieces to it on either side, putting in pockets as I did. It turned out very nice. I used an ivory satin for the finished side, and lined it with a gorgeous cranberry satin!
I'll have to get a good picture of her in it and send it to you.