Her contract was up and she had a better paying job offer, with better billing. It was a professional decision to leave instead of renewing for a one year contract.
She was on Becker for six (six?) years.
Terry stayed for 4 years.
The show lasted 6 years.
No idea why she couldn't last the distance this time?
But a year later after Becker, she's seemed to have given up acting.
Wikipedia says Farrell's retirement was about concentrating on her family and mastering Yoga.
horrible women for the franchise but if were talking just Voyager, erm probably Chakotay because after a few years he basically does nothing but crash shuttles.