My main complaint is the ending.
Consider that Picard starts this relationship. And then his problem is that after he sends Nella into danger, he realises that he can't face doing that again because she means so much to him. So be clear - Captain Picard is saying that he cannot do his job as Captain because of his own personal feelings for one of his crew.
And his solution to this is, the crewmember needs to transfer off the ship.
Um, Picard? No. Nella did her job and performed like a professional throughout. She is not the problem here. PICARD is the problem here. The solution to that situation is that Picard transfers off the ship.
Note that Picard has more than once told people under his command that if they have personal problems that get in the way of their duty, it's up to them to get the hell over it and do their duty anyway. Or, if they can't, to get the hell out so he can have somebody who can. Yet here, when it's him, that attitude goes out the window. And I don't really mind that - the whole point of the episode is that his personal feelings have overcome his usual discipline. Fair enough, we all have our limits. But what I don't like is that his response to that is to penalise somebody else for his failing. And the episode never so much as raises this point - the writers just took it for granted that she would leave.
Now of course the show is not going to fire Patrick Stewart. But they at least needed to address this in some way. In the scene where he tells her how he felt when she was in danger, he needed to say that he is going to apply for a transfer as he's the one with the problem. Then she can offer to transfer, voluntarily, agreeing to take the career hit so that Starfleet can continue to have its best captain on its best ship. That's a better ending because even though it's the same resolution, and still unfair to her, at least she is exercising her own agency and making a choice of her own.
Give a man a fire, and you keep him warm for a day. SET a man on fire, and you will keep him warm for the rest of his life...