Schmidt’s book is said to have contained clues linking Parton’s emotional attachment to bandleader Gregg Perry, although it did not establish the relationship was physical.
Parton said she had “cried an ocean” over the episode.
The singer repeatedly rejected suggestions her long marriage to Carl Dean meant either partner was free to have sexual relationships elsewhere.
She said in 2014: “Yes, it’s an open relationship, but not sexually, and I would kill him if I thought he was doing that. He would shoot me too. At the end of the day, we love each other madly.”
Parton and Dean met outside Nashville’s Wishy Washy Laundromat and married on May 30, 1966.
They later renewed their vows for their 50th anniversary.
Dean died in March 2025 at 82.
Trump paid tribute to Parton following Tuesday’s announcement of her death, describing her on Truth Social as “one of the greatest Country singers, and far beyond, EVER.”
He added: “This is a true loss for millions of people. There has never been anyone like her, and never will.”
Trump ordered flags lowered for one week, adding: “Rest in Peace, Dolly! The World loves you. President DONALD J. TRUMP.”