Camilla Tominey, of The Telegraph, reported that two sources told the newspaper that Kate was "in tears" following her three-year-old daughter's bridesmaid dress fitting.
An insider told the publication: "Kate had only just given birth to Prince Louis and was feeling quite emotional".
Kate welcomed Louis on April 23, less than a month before Meghan and Harry walked down the aisle on May 19.
So it wouldn't be surprising if she was feeling a little overwhelmed, especially as eldest son Prince George was also acting as page boy.