I am currently writing a very thought-provoking (at least for me) fic called To Cast Away Stones and someone recently asked how it's possible that Leia's adoption was not public knowledge. At several points in that story, there have been delicious moments of dramatic irony. Luke will claim Leia is his sister as part of a cover story or Leia will make some comment about her own parentage.

I've seen a wonderful conversation written by Bellebayard, JediSkySong and FernWithy/JediGaladriel in their fic "The Penitent". In it, Leia is talking to Anakin post-ROTJ and they are discussing their relationship. She says "Lord Vader, did I ever tell you I was adopted?" and from there, it takes all of four sentences between them to arrive at her heritage. I was very fascinated by that moment and the statement at the end: "May the Maker forgive me."

It begs the question of how close to knowing the truth Leia was at any given moment.

First consideration, I think, is whether or not she ran across her mother's name or holo. Obviously, since Padme was a prominent member of the Senate, at least by virtue of longevity. Leia probably heard stories about the fall of the Republic and especially how Palpatine came to power. This could have happened in school or at home as part of her upbringing as an Organa.

Did she ever look at a picture of that senator and recognize any of herself? If, as she tells luke in Return of the Jedi, she remembers "images, feelings" of her mother, would those images that she somehow gets give her a connection to the person she's seen in the holos?

Also, how paranoid would the Organas have been? Certainly, they'd have been careful to keep her from knowing about her father's fate.

Second of all, the EU suggests heavily that Leia is Force-sensive and even ROTJ Luke tells her that she has the same power to be a Jedi that he does. Was this suppressed? How was it suppressed? I believe very strongly that Leia's "resistance to the mindprobe" was an evidence of her connection to the Force, since it was basically fighting fire with fire.

I believe that she was told about her own adoption, but not the details, mostly because she did have those memories of Padme.