I have nothing against her. I was pleasantly surprised – and I wasn't alone – to learn that all my prejudices were wrong and she's a pretty good actress. Billie and Rose between them were exactly what the show needed to kickstart it in the twenty first century. When she felt it was time to move on with her career, she couldn't just leave. The producers rightly put Rose in a situation where she had to go, had to stay away and could not come back. Ever.
Except that apparently, she can. Thereby making that heart rending farewell on a beach in
I has a TARDIS gets it about right, here and here.
But – shows rely on ratings, ratings rely on actors, and as long as the actor is actually alive in the real world (and even then not always) there is always the possibility of their character returning. Producers should be made to hand over their firstborn child as a deposit against yielding to the temptation. It cheapens all that has gone before; it devalues any kind of tension.
Trek did it with their mirror universe. In the original series, in a one-off episode, a transporter accident sends our heroes into a parallel universe where they are evil (and their evil counterparts end up in ours). You can tell they’re evil because Spock has a beard, though fortunately for all he’s just as logical as usual and is key to the plan to get everyone home. And they really have to put their thinking hats on to make it work. It was a conundrum and a pretty good episode.
By the end of DS9, however, people started popping over into the parallel universe every time they put the wrong fuse in a plug. And then they started doing it at will. It had its compensations (evil Major Kira = woof!) but it was still cheap and lazy and diverted resources from doing something really creative.
One more reason why books will always be better ...