The love affair was first revealed in Tom Bower's biography 'Sweet Revenge: The Intimate Life of Simon Cowell' and although the book was officially unauthorised, Simon did speak to the author for it.
She told the British edition of Glamour magazine: ''I haven't read the book, but I've been told about the excerpts that relate to me and the speculation about my private life.
''From what's been reported they -- Tom and Simon -- put hundreds of hours into making this book, and Tom is a respected journalist.
''They looked very pleased with it all at their launch. I'm sure it makes for a great read and I wish them the best.''
Dannii also revealed she turned down the chance to return to 'X Factor' because of her commitments to 'Australia's Got Talent'.
She said: ''I was offered the chance to return, but I decided it wasn't the right thing for me. It didn't fit in with arrangements I'd made for 'Australia's Got Talent'.
''I have been with 'AGT' since the first episode and it's filmed in my home town. I had four incredible years on The 'X Factor' but the show has moved on and so have I.
'''The X Factor' will always have a special place in my heart. I'm still in contact with the contestants.''