The brunette beauty was all smiles while attending the launch of Millie's new clothing range, held at London West Bank Gallery in Notting Hill.
And of course, it was only fair she wore a piece from Mills' range!
Showing off her svelte figure, Rosie sported a form-fitting dress covered in an intergalactic print, featuring a black panel around the waist plus a peplum hemline for added interest.
If you want to snap it up for yourself, it's available to buy now at millie-mackintosh.com, retailing at £80.
Rosie totally upped the ante with her footwear too, pairing her fancy frock with metallic blue ankle boots which glistened as she posed for photographers.
The stylista stashed all her party essentials in a Lulu Guinness lip-shaped shoulder bag while adding a chunky gold watch and immaculate nude nail polish.
She also swapped her usual tumbling waves for a new 'do, slicking back the front section of her mane before securing with a hair slide and leaving the lengths to fall past her shoulders.
And we couldn't help but notice how dewy, radiant, and all-round fab the starlet's skin looked. Good thing we already know the secret behind Rosie's glow - find out what it is here!
What do you think of Rosie's outfit? Let us know by commenting below as the best comment across the site each week wins £50!
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