The two ladies enjoyed a girls night out this week, and Rosie took a snap of her friend as they sat down for dinner and drinks.
In the picture, newlywed Millie can be seen striking a pose, a cocktail in her hand.
"There's my girl. Dinner with @millsmackintosh," reality star Rosie wrote in the caption.
Proving just how close the two friends are, Rosie also shared a picture showing the pair wearing the same knee-high boots for their evening together.
Millie is still on cloud nine following her marriage to rapper Professor Green — real name Stephen Manderson — last month.
The happy couple tied the knot in a romantic countryside ceremony at Babington House in Somerset on 10 September.
Style queen Millie looked stunning in a vintage style Alice Temperley 'Bluebell' gown with a waterfall hemline a train and lace detailing around the shoulders.
Shortly after their wedding, the newlyweds jetted off on a romantic honeymoon to enjoy their first few days as husband and wife.