Trump was responding to a question from the press pool about Manigault Newman's tell-all memoir that was announced this week.
This was despite objections from White House chief usher, Angella Reid, who served under President Obama and was the first black woman to hold the post. In the book, she paints Trump as scattered, self-absorbed, misogynistic and insecure.
And Sanders is correct - both Manigault Newman and Trump once had a close relationship after she became a star contestant and popular villain on his hit reality TV show, "The Apprentice".
"Yeah. The Art of the Deal is a bestseller!" "I said, 'Instead of the Bible?'" she claims to have said.
"Unhinged: An Insider's Account of the Trump White House" reportedly contains a number of bombshell allegations against Trump from Manigault Newman's time in the West Wing, though some of them have been contradicted or widely discredited.
After his election she joined his administration as communications director for the Office of Public Liaison before leaving in January.
She says when she turned down the offer, she received letters from Trump's lawyers telling her to stay quiet.
She alleges that Trump has exhibited signs of a "mental decline that could not be denied" and says she went as far as printing out a study linking Diet Coke consumption to dementia and strokes and putting it in his briefing stack.
'During production he was miked, and there is definitely an audio track.
The White House has rebuked Manigault Newman's book, with Press Secretary Sarah Sanders calling it "riddled with lies and false accusations". "It's sad that a disgruntled former White House employee is trying to profit off these false attacks, and even worse that the media would now give her a platform".