Clarence House and Kensington Palace staff have form for leaking. The media campaign and leaking ramped up after the Sussexes had their very successful first foreign tour and again when the papers were hinting about William's possible affair* (he used human rights law to shut down the media).
*Which he may not have had
If I were Kate, I would be fucking furious with them.
Why? What have they done to her? Meghan wasn't even at Charlotte's dress fitting. It was originally reported as Kate crying there (new baby hormones, tears of happiness) and then H&M non fans saying Meghan had made her cry?? I find the royal rota papers rather misogynistic. Minus the Commonwealth Service, Kate has always seemed happy and at ease with H&M.
I remember when K&W became engaged, Harry said he was looking forward to getting to know her (he had spent some time with her, but didn't know her that much). He has also said (pre-Meghan days) that he and William weren't as close as people thought.
William and Harry were part of a small club (young British royals), which helped them understand their unique restrictions and difficulties... But they had different friend groups, different careers, lived in different countries, etc.
Harry wore the nasty nazi uniform during Prince William's rather offensive Out of Africa themed birthday party (his theme). It featured blackface, tribal costumes, witch Doctor custumes and banana costumes (!!).