The actress went all Downton Abbey on us in the slinky peach floor-length number that skimmed her stunning slender figure, however it was obvious that Ms. Miller decided to give her bra the elbow...
Is that nipple we spy? Whoops!
In spite of her little wardrobe malfunction, Sienna looked every inch the vintage siren in the trailing gown as she offset the striking look with a slick of deep red lipstick and bushy, bold brows.
Her bob-style tresses were slicked back into an effortless yet oh-so-chic chignon bun which was pinned to her crown for a prim and proper yet super-stylish vibe that wouldn't look out of place at Fashion Week.
Where's the catwalk when you need one?
A simple silver necklace and crystal studded earrings were all the blonde beauty needed to complete her gorgeous getup as she posed for the paps ahead of the 'High Rise' premiere in sunny Spain.
Totally smashed it right? Even sans the undies!
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