It is an usual hairstyle for Charlotte, who usually wears her locks half-up half-down, or parted to one side. She will be at Westminster Abbey to celebrate the 100th birthday of the Royal Air Force that includes a flyby from various aircraft over Buckingham Palace.
The 92-year-old monarch has a busy week ahead, marked by a visit from US President Donald Trump in Windsor on Friday.
Charlotte, three, was seen sporting the new style while attending baby brother Louis' christening at St James's Palace, London, on Monday.
His parents, the Duke and Duchess of Cambridge, his siblings, Prince George and Princess Charlotte, his grandparents, the Prince of Wales and the Duchess of Cornwall were in attendance among others.
Kensington Palace reports that following the service, Wills and Kate hosted a lovely tea for guests back at Clarence House.
While they obviously hold the titles of Louis' aunt and uncle, the couple have missed out on being named as godparents.
Britain's Prince Louis of Cambridge, the baby son of Prince William and his wife Kate, was christened on Monday, July 9, but Queen Elizabeth II did not attend. Charlotte wore a pretty sleeveless floral sundress in pink, and she wore the same shoes as George, but in a cute pastel pink.
And little Charlotte couldn't resist sticking her tongue out at crowds while stood alongside her brother - who also pulled a face or two.
Meghan, Duchess of Sussex, went the Kate Middleton way of things and wore a single colour head to toe. Picture: AAPNicholas van Cutsem is another godparent.
Pelly is another lifelong friend of William and Harry's, TIME reported.