Markle, 37, reportedly requested to wear a jeweled tiara from the Royal Collection for a state dinner in Fiji with Prince Harry in October, but Prince Charles nixed the idea for fear of the Duchess of Sussex appearing "extravagant," insiders told The Daily Mail.
The same evening, for a state banquet at Buckingham Palace, Middleton, 37, wore a diamond and pearl tiara previously owned by Prince William and Harry's late mother, Princess Diana.
"Meghan did not understand all of this because she was new to the role and so Prince Charles told her that it would not be appropriate," a source said. "It was very kindly done."
The source noted that Prince Charles advised Markle against the idea because of the low socioeconomic status of much of Fiji compared to the riches of the royal family.
It reportedly wasn't the only time the former "Suits" actress was denied a luxury headpiece.
The jewels in the emerald tiara allegedly couldn't be traced and may have been from Russia.
The Queen instead lent Markle a diamond and platinum tiara from her own collection.
Princess Eugenie wore an emerald tiara for her own wedding in October 2018.