My summation was that Farrell left because the studio refused to negotiate with her and Berman used misogyny to demean her.
In the doc, she clearly states that that she felt no one was willing to "have a conversation" about her contract. In 50YM2, and in other interviews, Farrell talks about the "take it or leave it" offer, which she found unacceptable. She suggests that Berman was unwilling to talk to her. She also says that his secretaries demeaned her during this period, saying she had a small chest and she would be working at K Mart if it weren't for Star Trek.
In interviews, she says that is was years later when she first taller to Behr about the negotiations, at which point, in her words, he nearly vomited. In 50YM2, she says that she never discussed her wishes with Behr. Also kn 50YM2, Behr says he was kept in the dark about what was going on by both Berman and Farrell. He supposes that it is because everyone feared he would be enrage by what was happening.
On the Delta Quadrant podcast in 2013, Farrell says that she felt that she was more valuable to the show, which should either be reflected in her contract or she should be allowed to do work outside the show.
To whom did Farrell relay her request to be recurring? To Berman, who was probably not inclined to agree to it?
Of course, Berman has said little about this other than to deny the misogyny. It still leaves my summation largely intact.
Unfortunately, I think people get too wrapped up in why Farrell left. It's sad to hear her answer the same questions over and over. Fans should forgive her rather than continually ask her to justify her actions. She doesn't owe it to us to be Jadzia Dax for the rest of her life. She was, and is, entitled to do what was best for her and for her career. People leave television series. It doesn't need to be a big deal.