Millie's current beau Hugo Taylor also made an appearance at the star studded bash.
The reality babe turned fashion designer looked breathtakingly beautiful as she slipped her catwalk-worthy figure into this eye-wateringly low-cut jumpsuit that boasted a nearly see-through lace top and skin-tight cigarette trousers to boot.
Millie - who has a bit of a penchant for plunging numbers - steered clear of an embarrassing wardrobe malfunction and teamed the rather risqué number with a matching but barely there lace triangle bra that drew attention to her teeny tiny waist.
As not to steal the attention away from gorgeous Rosie, Millie co-ordinated her sleek and chic ensemble with a failsafe pair of black court heels and her trademark quilted Chanel bag. The stunning star gave us a major case of hair envy with her impossibly glossy, caramel-coloured locks which she wore in an effortlessly tousled blow-dry.
Millie - who recently divorced from husband of two years, Professor Green (real name Stephen Manderson) - was soon joined by Hugo and the pair rubbed shoulders with pink-haired Amber Le Bon and Lady Kitty Spencer.
At the time of Millie and Professor Green's split, the pair insisted it had been a "mutual decision." They released a joint statement which read: "It is with sadness and regret that we confirm our separation.
"It is a mutual decision. We still care deeply about each other and would like it to be known it is on amicable terms and we wish each other well."
Since then, Millie has been pictured kissing ex-Made In Chelsea star Hugo Taylor confirming their romance.
Follow us on Twitter @RevealMag for all your celeb, fashion and beauty news!
Fancy winning some GREAT prizes? Check out Reveal Competitions here!