Ms Cohen was reportedly hand-picked for the job of royal adviser to Meghan, as she transitions into her new life as a duchess, after rising through the ranks from the Buckingham Press Office to private secretary for the Queen.
Robert Jobson, royal biographer, claimed in his new book Charles At Seventy, that the Royal Wedding preparations were so stressful that Prince Harry became “petulant and short-tempered” with members of staff.
Jobson writes: “Raising his voice on occasion, Harry would insist: ‘What Meghan wants, she gets’.”
The news of the staff's resignation also comes amid claims the Queen warned Harry about Meghan's "difficult" attitude after a row over what tiara she could wear on her big day.
A well connected Royal source said: “Meghan had her heart set on this tiara with emeralds and Prince Harry hit the roof when they were told it was impossible for her to wear it.
“There was a very heated exchange that prompted the Queen to speak to Harry.”
The source claimed: “The message from the Queen was very much Meghan needed to think about how she speaks to staff members and be careful to follow family protocol.”
Melissa and Mrs Cohen's resignations follow that of Edward Lane Fox, who was formerly Harry’s “right-hand man”, but quit in recent months after 15 years in the job.