Esters said she thought Kelley had been working with Harvard Professor Henry Louis Gates, who was tracing the Winfrey family's roots, when she talked to Kelley in 2007, the New York Post reported Friday.
Kelley quotes Esters in the book as saying she knows the true identity of Winfrey's father.
"I'm sorry this book portraying (Winfrey) falsely was ever written and that I participated by answering questions," Esters said.
"Kitty Kelley misquoted me when she said I told her who your father was," Esters said she wanted to tell Winfrey. "'How could I know?' That's all I'd want to tell (Winfrey.)"
Kelley also says in the book Winfrey abused drugs and exaggerated the extent of the poverty she endured as a child, media reports have said.
Winfrey has commented little about the book she described as "a so-called biography," other than to predict, "This, too, shall pass."