With cut-out panelling on the bodice, Millie was leaving little to the imagination as she showed off her super slim body in the gorgeous gown.
One thing's for sure - Millie shouldn't lose any more weight!
Millie's been taking no chances in preparing for her red carpet appearance, taking on a special BAFTA fitness regime.
Millie recently posted an Instagram pic of her ab-ulous bod in just a bra and yoga pants along with the caption: "2 weeks into training with richtidmarsh #leanmeanmission #nopainnogain #byewobblybits."
Her personal trainer also tweeted a photo of her impressive workout.
The teeny tiny TV star is, of course, also getting ready for her impending nuptials to rapper Professor Green.
We can't imagine she could need to go on any sort of wedding diet with those abs!
Fashion conscious Millie also tweeted from the red carpet about the inevitable difficulties of combining glamour and the Great British weather!
She posted: "Wind and rain + a dress with slits = wardrobe malfunction!"