If it Lucas Luke and Leia were going to be siblings from the very beginning, I do feel like he would’ve handled it differently. Yes, the trilogy is more so Luke’s story than anyone else’s, but the revelation and what it means for Luke isn’t given the same weight for Leia, even if the implication is pretty much the same.
Of course, Luke idealized his father, wanting to be like him, so discovering what his father became has this consequence of Luke wondering if he could become that too. Whereas when Leia was adopted by the Organas, they raised her as her parents. So I don’t think Leia ever spent much time wondering who her biological parents were, or wanting to be like them. The Organas were enough for her to look up to.
I know the EU and Canon both explore Leia’s feeling on Vader being her father a little, but it could’ve been interesting for the movies to explore that more.
There is a very strange, almost serendipitous scene in Empire Strikes Back that has always fascinated me. It happens after the scene where Chewie flips out and starts attacking Storm Troopers just before Han is about to be lowered into the carbon-freezing pit. Han intervenes and tries to calm Chewie down before things get out of control. While this is happening, Boba Fett aims his blaster at Chewie, but then Vader stops him from firing by pushing down the barrel of his blaster. Then - there’s this weird shot of Leia just staring at Vader for a few seconds. This is followed by a shot of Vader, seemingly staring back at her (although we can’t tell for sure because of his mask). Leia then walks over to Chewie and starts trying to calm him down. It’s the strangest thing, as if Leia and Vader instinctually exchanged some non-verbal agreement to prevent the situation from escalating further.
I know it can’t possibly mean much. The idea of Leia being Vader’s daughter didn’t exist when that scene was written and filmed. But it’s another one of those uncanny, serendipitous coincidences that takes on an interesting new dimension retroactively in light of later revelations.