Audrey’s character gives an audience to the press in Rome, the epitome of early 1950s ‘ladylike’ ideal. She wears what appears to be a lace overdress, with shawl collar, belt and surplice bodice. This is worn over (presumably) a solid white underdress/slip with full petticoat.
Making an entrance:
The back. Note the dropped waist (or probably a hip yoke) that is more pronounced at the back than it is at the front:
Halfway down the back, the start of the underdress is just visible: