The pretty brunette joined her former castmates - including Binky Felstead, Oliver Proudlock and Lucy Watson - while launching the Thomson #MyScene campaign.
Millie - who arrived without hubby Professor Green - showcased her take on effortless evening style, sporting a pretty flouncy dress covered in a cute blue and white floral design.
The starlet warded off the chills by sporting a pair of black opaque tights, while amping up the va-va-voom with racy suede over-the-knee boots.
We love her thigh-high boots, but unfortunately they're pretty pricey, retailing at £595 from Russell & Bromley (and her pal Rosie Fortescue has them too!).
To complete her ensemble, Mills wrapped up warm in a thick black coat while toting a chain strap bag on one shoulder, accessorising with a few sparkling rings.
And Millie also took the opportunity to show off her new barnet, after visiting the salon earlier that day for a hair refresh.
Taking to Instagram to showcase a photo of her freshly-cut locks, the starlet wrote: "Thank you for rescuing my hair @miguapo78 @joshwoodcolour! Ready to go out tonight."
We're definitely suffering from a serious case of hair envy right now!
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