Speaking to BBC Newsnight, Ms Wolkoff said: “Melania to everyone else is an enigma.
“Melania has this wall around her, it’s impenetrable, it’s steel. It’s kept her mysterious to the world.
“Nothing behind that is what represents the true Melania. The mysteriousness, the ability to keep that wall up has enabled her to keep this mystique.
“This sphinx-like being that everyone is wondering if that is really who she is and it’s lead to a lot of conversations, ‘Is she a victim? Is she locked up? Is she going to divorce him?’
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“The reality is perception for the Trumps is everything, we know that.
“It’s been written about by Ivanka’s own words.”
BBC presenter Kirsty Wark asked: “You describe their engagement in 2004 as either a magic moment or making a deal. Is it a transaction? Do you believe that?”
Ms Wolfoff replied: “I do believe it’s a transactional marriage.
In a statement to The Washington Post, Ms Grisham labelled the book as “revisionist history.”
She also claimed Ms Wolkoff based the book “on some imagined need for revenge.”
Ms Grisham added: “Literally everyone she worked with was an obstacle in her mind, people she belittled and blamed for everything.
“This is a deeply insecure woman whose need to be relevant defies logic.”
“Anybody who secretly tapes their self-described best friend is not only dishonest, they’re deceitful.”
In a previous statement to Politico, Ms Grisham also said: “This book is not only wildly self-aggrandizing, it’s just not truthful. It is an exercise in bizarre twisting of the truth and misguided blame for the sake of self-pity. It’s unfortunate and concerning that she’s overstated their friendship and her very brief role in the White House to this degree.”