"Thank you everyone for your lovely messages on The Duchess of Sussex's birthday", Kensington Palace added.
The tweet came after Samantha had joked about her sister and Prince Harry's intention of retreating from the media - calling Meghan Cruella DeVil.
The Duchess of Sussex showed up to the ceremony in an elegant yet affordable dress from Club Monaco, pairing her royal ensemble with a pair of Aquazzura pumps, a fascinator by her preferred milliner, Philip Treacy, and a Kayu clutch with a gold clasp.
Samantha and Meghan haven't been in contact for years - but that hasn't stopped the Duchess's sister from weighing in on Meghan's life.
Van Straubenzee and his older brother Tom are two of Prince William and Prince Harry's oldest friends; Tom also serves as Princess Charlotte's godfather.
He is also thought to be known as "Spike" amongst the Duchess and her friends.
Prince Harry and Meghan, who have been spending their spare time at their country home in the Cotswolds, will be joining Queen Elizabeth shortly at Balmoral for the annual royal family summer visit to the Scottish Highlands.
Meghan Duchess of Sussex arrives to attend the wedding of Charlie van Straubenzee and Daisy Jenks at St Mary the Virgin Church in Frensham England
Late this summer, Meghan is expected to return to the US on a private plane to spend time with her mother and friends.
Meghan spent her first birthday as a member of the royal family seeing van Straubenzee and his bride Daisy Jenks tie the knot.
"Harry and Meghan have tried ignoring the Markles, but it's not working".
See more of her look here.
"For someone to say you should turn down a paycheck...tell your boss that you don't want a paycheck".
They aren't the only Royal couple thought to have nicknames for one another. "And hopefully we'll start a family in the near future".
"I think a lot of the public is concerned, like, 'Why are you utilizing public channels?'" she continued.