This is a first. Not only has Sienna copied what instantly became a classic as soon as Gwyneth wore it to the Oscars, but she's copied it badly. I mean, it's not awful, but it's no Tom Ford. And if you were wearing a statement white dress that was going to be compared to Ford's, you'd want it to be special. She's done the double cuff thing, which I love, and that tiny, lip shaped clutch is perfection, but really, too many women are attempting to pull off the cape only to end looking more like Endora from Bewitched than modern superhero. Sienna falls in that pile I'm afraid.
Just in case you forgot how fab Gwyneth looked:

In a class of her own.