Originally Answered: Star wars?
There is one fundamental thing you have to remember about Lucas ... he changes his mind seemingly with the direction of the wind. I've seen him give two different answers to the same question in the SAME interview. His favorite words, other than faster more intense, are "My words were taken out of context".
As "ggtk7" says this little "opps" in the storyline has been the source of much very heated debate among fans but Lucas has actually answered this question ... he says that Leias "memories" of her mother were Force generated because of her traumatic birth. When asked why Luke, who was born first, doesn't have any such memories he says that it's because he is the "sword" of the twins and that Leia is "emotional" one. Now this does kind of fit in the story but it is a pretty thin kind of reasoning ... at least it can be somewhat reasoned out unlike the "Ghost Switch" at the end of Return Of The Jedi where he switched the Force Ghost of Anakin with Hayden instead of the guy who was originally there. His reason is that Anakin died when he became Darth Vader. Even the data banks at starwars.com don't match with what he says because there it says that Anakin died in the arms of his son on Death Star II. Welcome to the world of George Lucas.
"ggtk7" also quotes Lucas from a recent interview ... I remember seeing it and having smoke pour out of my ears because this is another direct contradiction of what he has said and done in regards to the Star Wars EU (Expanded Universe of books and comics) and he knows it. That being said this IS his story and what he says is what it is but the only thing in that statement that is really true is that Star Wars has become to big for one person to keep track ... that's why he has delegated the content of the books and comics to a couple of his most trusted "people" ... Sue Rostoni & Lucy Autrey. Those two are the ones who keep the books and comics from "clashing" with what has already been written and even then major story lines MUST be approved by Lucas. I must say I'm sorry to anybody who hasn't read the New Jedi Order story line yet but there is one thing in the first book of the series that prove Lucas does have a hand in the EU. The first book of that series is called "Vector Prime" and in the original drafts of the book Luke Skywalker dies in it ... Lucas gave that a big NO WAY so instead of Luke dying in that book Chewie does. I really don't think that Lucas could give specific answers to any of the goings on in the books but Lucy and Sue keep him up to date with what is going on in the books.
In the end it all comes down to being one of the many "Only George knows" kind of things and sometimes he doesn't.
May The Force Be With You ...
PS: Just a small comment about one of the other answers given by "RiKoLoVern_JOEJONAS_LoVeR:
Every hear the old saying "calling the kettle black" ... you call us "nerds" and obesess about Star Wars ... doesn't your nickname here show massive obession with the Jonas brothers ... just a thought.
Originally Answered: Star wars?
This has been an ongoing discussion and the only answers that can be found are fan speculation.
I think maybe Leia is actually recalling her own adoptive mother on Alderaan. That is the best answer that I can give myself.
There are a lot of convoluted "connections" between the original trilogy and the prequel trilogy. Unfortunately we have to take the movies' cannon with a grain of salt because Lucas was not able to tie the loose ends together as solid as hoped. Lucas has a broad outline on how the story arch should go, but had not really written the scripts in their entirety until pre production time came around.
So the short of it, we got to live with it, or read some of the novels out there to fill in the gaps of the befores, the durings, and afters, of the SW universe until we decide as fans what satisfies us as an answer.
To George Lucas, for his responsibility to the cinematic storyline, his word is canon.
George Lucas wrote:
But there's no story past Episode VI, there's just no story. It's a certain story about Anakin Skywalker and once Anakin Skywalker dies, that's kind of the end of the story. There is no story about Luke Skywalker, I mean apart from the books. But there's three worlds: There's my world that I made up, there's the licensing world that's the books, the comics, all that kind of stuff, the games, which is their world, and then there's the fans' world, which is also very rich in imagination, but they don't always mesh. All I'm in charge of is my world. I can't be in charge of those other people's world, because I can't keep up with it.