In Mark A. Altman and Edward Gross' oral history book The Fifty-Year Mission: The Next 25 Years, From The Next Generation to J.J. Abrams by Edward Gross and Mark A. Altman, Farrell explained why she left DS9. "The problems with my leaving were with Rick Berman," Farrell explained. "In my opinion, he's just very misogynistic. He'd comment on your bra size not being voluptuous.... That stuff was so intense, especially the first couple of years." The actors signed six-year contracts, so leading into the seventh and final season, Farrell asked for her role to be recurring, telling Gross and Altman she would've appeared in 13 out of the 26 episodes.
"Rick Berman said I was hardballing him," she said, but characterized her own desire to "just have a conversation." The negotiations got nasty, however. Farrell said a junior producer told her without Deep Space Nine she would "be working at K-Mart." She also said the producer would call her right before shooting scenes to ask if she'd made the decision to sign a new contract. "Basically," she said, "he was trying to bully me into saying 'yes.'" Behr, the showrunner by this point, said he was completely in the dark about Farrell's trouble with Berman. He implied that he would've stopped her firing from happening at all or, possibly, have left with her.
https://www.cbr.com/star-trek-why-terry-farrell-jadzia-dax-left-ds9/