The Sussex's new biographical book claims to reveal details of the fallout between Meghan and Harry and the Cambridges, suggesting the Queen didn't approve of their decision to quit and says Prince Charles gave them a "warning".
In a witness statement submitted to the High Court, the duchess said Associated Newspapers, the publisher of the Mail on Sunday, was "threatening to publish the names of five women". He said removing their names "would be a heavy curtailment of the media's and the defendant's entitlement to report this case and the public's right to know about it".
The book claims he told Harry: "Take as much time as you need to get to know this girl".
The Mail on Sunday's publisher Associated Newspapers Ltd (ANL) won the first skirmish in the legal action on May 1, when Mr Justice Warby struck out parts of Meghan's claim, including allegations that the publisher acted "dishonestly" by leaving out certain passages of the letter.
Neither Harry nor Meghan was in court for today's hearing.
However, she argued, Harry never quite felt at ease.
In an extract from Finding Freedom, authors Carolyn Durand and Omid Scobie write of an episode in December 2016: "She was advised that wearing such a necklace only served to encourage the photographers to keep pursuing such images and new headlines".
According to a friend cited in the book, "Harry could see through William's words".
The High Court yesterday heard the Duchess "freely" and "without being compelled" disclosed the identities of the five friends whose privacy she now fears will be breached.
In an embarrassing moment during the application Mr Rushbrooke accidentally let slip the surname of one of the five. Associated Newspapers says the friends' evidence "is at the heart of the case" and their identities should be known.
Justin Rushbrooke QC, barrister for the Duchess, told the High Court that she had been forced to identify her friends in a legal request by Associated Newspapers and added that the five were entitled to "a very high level of super-charged right of confidentiality".
She further added: "I think Meghan has very much been the catalyst in giving him that confidence to break free from William and Kate and to break free from that trio dynamic, which was at times cosy and convenient, but actually wasn't really what he wanted".
In written submissions, Antony White QC, acting for ANL, said: "The friends are important potential witnesses on a key issue".
In court documents outlining her claim against the publisher, her solicitors say the letter was "obviously private correspondence" and she did not expect the contents to be made public.
Mr Justice Warby reserved judgment and said he hoped to make a ruling on the friends' anonymity by mid-August.