Shockingly, the royal author went on to say that Prince Harry's mother, the late Princess Diana, would be "appalled."
"She had enough nous to know when to put on a show," Campbell - who claimed to be a confidante of Princess Diana - sniped.
The barbs came just days after she slammed the actress for trying to "hustle her way to the top."
On Monday, Lady Colin Campbell told Good Morning Britain that while she is rooting for the Duchess, she has an "awful feeling" about her future and believes Meghan needs to learn to behave like a member of the royal family.
"I have an awful feeling that Meghan needs to understand things she doesn't yet understand," she told the morning show.
"Like there is a massive difference between being a celebrity, hustling your way from the bottom to the top, and she was a very proud hustler."
The I'm a Celebrity Get Me Out of Here star dug the knife further and brought up Meghan's first husband, Trevor Engelson.
"She used to use the word hustle for herself and her first husband, very proudly."
The Diana, Princess of Wales author made several suggestions for the Duchess of Sussex to work on.
"Being a royal; you don't hustle, the values, embodiment is completely different, she's sorted, she's got it, I think she needs to now embrace it and understand it's a new game in town. She's an actress, she needs to come up with a new act!"
The Sussex Royals have not commented on the author's words.
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