The Fifth Element star was at the event with Resident Evil: Afterlife co-star Ali Larter and admits she should have thought about wearing something different.
She explains, "It was short. I shouldn't have put my arm around Ali Larter like that. I was not even thinking my dress was hiking up.
"Roland Mouret is the man but I should have experimented a little more in front of the mirror. Now I know: never put my arm around anyone!"