I saw the tour in Philly as well, and I didn't notice any difference in her dress after the trapdoor... I was sitting Family Circle, SL, practically in the lighting fixtures, so I could see lots of details (even though I was a tad high, I was really close). If it is a different dress (and I'm just oblivious) I would assume she has the simpler dress on under the more elaborate dress, to allow a quick change. I could be totally off the mark, though.
"It's not for sissies, contrary to popular belief." - Tommy Tune, on musical theatre.
My avatar: Yummy, no?