From Page 586 of the Deep Space Nine Companion
Of Farrell's decision to leave the show, the actress says simply, "My heart said it was time to move on. After playing the character for six years, there's things I wish we would have done. I wish I would have had at least one fight scene this year. But there's nine major characters, so the writers can only do so much." Farrell admits, "I've had six years and one hundred fifty episodes of experience on this show, so my sadness is more in saying goodbye to the people. I don't feel cheated out of the character in the same way as I would have if the show had been cancelled, because I've gotten the opportunity to play her. And besides," she says, "it's Jadzia that's dying. Dax is living."
The book was published one year after Deep Space Nine went off the air. The author had unprecedented access to actors, writers, producers, etc. when writing this book while the show was still on the air. Don't you think if there had been any disagreements between Farrell and Berman or anyone else, she or the producers would have taken the time to mention something while the book was being written?