Royal fans immediately flocked to the image to share how much they thought the youngster resembled Princess Charlotte.
"Princess charlotte looks like you!" while another added "I thought it was princess Charlotte for a moment".
Another posted: "Princess Charlotte has the Spencer genes. You look so similar on this."
Kitty is the eldest daughter of Earl Spencer, Diana's brother, and his first wife Victoria Lockwood.
She has remained close to Prince William and Prince Harry since Diana's death, attending both their weddings.