The friend told DailyMailTV that Meghan had a feeling that she was "catching". Samantha announced in April 2016 that she would go out with a book & The Diary of Princess Pushy's Sister, but then changed to her Shadows of the Duchess. It is believed to be released in April, around the same time that Meghan is expected to give birth.
Samantha said the book "covers everything from behind the scenes that the world does not know."
He recently published plans for a second book.
Megan's friend said that she has now stopped interviewing her family members and hearing about herself.
They said: "I stopped reading things after finding out about her sister's book.
MORE MORE BOOK: Meghan Markle and Prince Harry look for the OTHER home
"Miss her when she got out of it.
"Out of all that was said, the same thing would disturb her in the book.
"She and Samantha had never had a very good relationship and she has a feeling that her sister uses her for a profit."
Meghan, now pregnant seven months, has been deceived by her sister in 2008 and her brother, Thomas Markle Jr. in 2011.
Both have spoken publicly about their Royal sister, especially to ask her to get out to her father, Thomas Markle Sr.
It was taken from Duchess Sussex since his Royal Queen was lost in May last year.
He had been involved in a scannal on paparazzi photographs held in the months before the wedding.
Mr Markle has been interviewed several times on television and in the media, saying he does not talk to his daughter.
However, her Duchess' relatives opposed this story in an interview this week, saying that it was on the other side – that Meghan tried to contact to her father and to be convicted.
They also said that he responded to a sensible letter asking him to stop attacking her in the media with a note asking for photos.
DailyMail.com's supervisor comment: "It's not fair what he did. He is always familiar with how she will contact her and have never been so close.
"As far as she got her job on Suits, he moved to Mexico and so they would not see each other just through the holidays."
Samantha answered the Tiwtter bids, called "bull ***".
She said: "There are plenty of text messaging and receipts to be confirmed in another way. Stop the #Fake news of PR crap."