When the book came out, Sharon denied that she ever said it. Only problem was, there was one other person there when Kitty was listening to Sharon. According to the New York Times (registration required):
Doubleday, the book's publisher and part of the Random House division of Bertelsmann, said it stood by Ms. Kelley's reporting. The publisher said in a statement that Ms. Kelly met with Ms. Bush for a four-hour lunch on April 1, 2003, where an unnamed third party heard the conversation, and that Ms. Kelley's editor, Peter Gethers, discussed the same material with Ms. Bush over the phone.
Lou Colasuonno, a former publicist for Ms. Bush, confirmed that he was the third party at the lunch and contradicted her denial. "I have not seen the book, I have only seen news reports," Mr. Colasuonno said. "According to what I have seen, what has been reported, I would not dispute that."