Katie Nicholl wrote about Queen Elizabeth and Meghan Markle's relationship in her upcoming book.
In "The New Royals," she said the Queen scolded Meghan during a tasting for her wedding.
The Queen was also "surprised" by Meghan's wedding dress, according to an excerpt from the book.
Queen Elizabeth and Meghan Markle clashed ahead of her 2018 wedding to Prince Harry, according to a new book.
The Mail on Sunday published an excerpt of Katie Nicholl's upcoming book, "The New Royals: Queen Elizabeth's Legacy and the Future of the Crown," and the sneak peek included details about Meghan Markle's early days in the royal family.
Nicholl wrote that there was tension in the royal family in the weeks and months ahead of Meghan and Prince Harry's wedding.
Meghan told Oprah Winfrey that Kate Middleton made her cry the week of her wedding over Charlotte's flower girl dress. But according to Nicholl, Meghan also clashed with the Queen during the planning process.
According to the excerpt, a source told Nicholl that Meghan got "quite upset" with a staff member during a menu tasting for her wedding at Windsor Castle when a dish that was supposed to be vegan tasted of egg.
Meghan and the staffer had a "tense exchange" until the Queen intervened, Nicholl reported.
"Suddenly the Queen walked in and said, 'Meghan, in this family we don't speak to people like that,'" the source told Nicholl.
The excerpt did not include details on what Meghan said to the staffer that caused the Queen to step in.
Queen Elizabeth was also surprised by Meghan's choice of wedding dress, according to a source who spoke to Nicholl.
"The Queen was surprised that Meghan wore pure white on her wedding day," a source told Nicholl for the book, pointing to the fact that her marriage to Harry wasn't Meghan's first.
Meghan was previously married to producer Trevor Engelson.
"Perhaps it's a generational thing, but she believes if you've been married before, you wear off-white on your wedding day, which is what the Duchess of Cornwall did," the source went on to tell Nicholl.