I personally think it was daft leaving one of the best TV shows ever to go to some bland, mediocre sitcom but that's show business and these things happen. These people don't owe us anything and are just doing their jobs.
From her perspective, she got more years of work out of it. She did Becker for 4 years, 3 years after DS9 ended. Except for William Shatner and Patrick Stewart, how many other Star Trek actors have gone on to have that much acting work after their show ended? And even though it was a mediocre sitcom, it was on a big network so she probably made more money, and I'm sure she thought it would be better exposure for getting more jobs.