It has been reported by the Daily Star that the working title for Samantha's book is "The Diary of Princess Pushy's Sister".
Grant has since stated on Twitter that her forthcoming book on Prince Harry's girlfriend of seven months is not "embarrassing".
'It's why nobody talks to her and hasn't for a long, long time.
Mum-of-three Samantha, 51, added: "It was something she dreamed of as a girl when we watched the royals on TV".
American actress Meghan Markle first splashed into headlines around the world past year when it was announced that she was dating the world's most eligible bachelor, Prince Harry of Wales. "I am very serious when I say she has dogged on Meghan forever", she explained. "Meghan has never done anything to her and continues to take the high road".
"When news broke that Prince Harry was dating Meghan, most people's first reaction was 'Who?' quickly followed by 'Oh, she's lovely, and oh my God, I need her coat, '" explains Dishaw of the reason for starting the website.
The estranged mother also made some controversial statements about Grant, revealing her alleged true colors.
"Samantha Grant doesn't have a relationship with Meghan Markle and she never has", a source told E!
The humanitarian is close with her father, who regularly visits her in Toronto, where films Suits and reportedly knew about the relationship from the outset. She called out Markle's "hypocrisy" and said Markle had a "hardened heart".
Their brother Thomas Jr has pleaded with her to "leave Meghan alone already", while her mother Roslyn has labelled the proposed claims as "bull***". So it doesn't sound like she'll have nice things to say about Markle.
"So you'll admit you're using your sister's fame and her name at the moment to sell this book, which isn't anything to do with her?"
"My book deals with my biracial family in a candid, warm, personal, and socially important way", Grant said.
"I think she believed the tabloids that I was writing a 'tell-all" book. I'm an older sister, not her gossipy little peer.
"I was there [at the time] and right after Meghan was born, she moved out and never came back".
Roslyn, 71, of Albuquerque, New Mexico, told DailyMail.com: 'She trashes Meghan, trashes me, her dad, her brothers - she's just been trashing everybody in her life forever.
She said life "wasn't always easy".