This venue for the event is currently being decided and will most probably be in a centralised location so that everyone can make it to the event with proper planning.
It was possible that she was trying out a Moulin Rouge ensemble that evening or perhaps auditioning for Cirque du Soleil.
When premiere night arrives, most stars go for the glamor choices because they know the cameras will be everywhere and they want to look their very best.
It's strictly speculation at this point.
She has consistently picked terrible choices for prestigious events.
Throughout that time, we have witnessed some major mistakes as well as some fashion faux pas incidents.