Star Wars may have finally explained why Leia was able to remember Padmé despite her mother dying moments after her birth. In Return of the Jedi, Luke talked to his sister Leia about their mother. According to the adopted princess, her mother died when she was young, and all she can remember are images and feelings. "She was very beautiful," Leia told Luke. "Kind, but sad."
The dialogue made perfect sense in the context of Return of the Jedi. In the 1983 film's novelization, James Kahn expanded upon this to suggest that Anakin didn't know his lover was pregnant when he became Darth Vader; after their birth, the last of the Jedi decided it was too dangerous keeping the twins together and so Luke was taken to Tatooine by Obi-Wan, while Leia went to Alderaan with their mother. George Lucas ditched this approach in Star Wars Episode III: Revenge of the Sith, revealing that Padmé died during childbirth. How could Leia possibly remember Padmé? If it was some weird Force-ability, why didn't Luke have similar memories?
After all these years, the latest Star Wars book - Queen's Shadow by E.K. Johnston - may have provided an answer. The book explores the relationship between Padmé and her Handmaidens, including Sabé - the decoy queen of Star Wars Episode I: The Phantom Menace who was played by Keira Knightley. After Padmé's death, Sabé and her lover Tonra decided that they weren't willing to simply watch from the sidelines as the Republic became the Empire. They were still grieving when they were contacted by Senator Bail Organa, who at this point in the timeline was contacting people he could trust in order to begin the Rebellion.
This idea is actually lifted from the old Star Wars Expanded Universe. According to Star Wars: The Force Unleashed Campaign Guide, after Padmé's death Sabé dedicated herself to opposing the Empire. She joined forces with Bail Organa, and became one of his key envoys, traveling the galaxy and establishing resistance cells. What's more, she also helped bring up the young Princess Leia, tutoring her in matters of court etiquette and diplomacy.
Assuming that something similar happened in the new Star Wars canon, it's possible this is the source of the confusion; Leia wasn't remembering Padmé at all, but Sabé. They obviously looked enough alike that Sabé could imitate the Queen in multiple high-stakes situations, and as close friends, she could impersonate Padmé effortlessly. And, given that Bail knew how close Padmé and Sabé were (and that the former Handmaiden had long since proven she could keep a secret), it's entirely reasonable to assume that she would be numbered among the trusted few who knew the truth about Leia. It's quite a beautiful thought that Padmé still had a presence in Leia's upbringing.
Supporting this theory is the fact that Sabé doesn't appear elsewhere in Lucasfilm's new Star Wars canon. She's most notably absent in Leia, Princess of Alderaan, a novel by Claudia Gray that explored Leia's early days in the Senate and revealed how she first became involved with the Rebellion; Leia discovered some of her father's closest allies - and Sabé wasn't among them. Given opposing the Empire was a dangerous business, it looks as though Sabé didn't survive into Leia's teenage years. Just as Leia half-remembered, she died when the Princess was young.
UPDATE: James Kahn, author of the Return of the Jedi novelization, reach out to provide added clarity to the backstory provided in his book:
"The point raised here about Anakin - in Return of the Jedi - not knowing Padme was pregnant when he became Darth Vader, so the twins were later separated for their safety and taken to different planets and foster parents - that’s the last remnant of a backstory for Leia that I wrote in the first draft of ROTJ. In writing the novelization I’d felt Leia was getting short shrift somewhat, so I invented a whole elaborate backstory about the circumstances of her birth, and subsequent upbringing on Alderaan. It was the one thing I wrote that got cut, or I was told to lose when writing the second draft - because, unbeknownst to me, of course, George Lucas had his own ideas about her origin story. The nerve! I dutifully cut the section - but the reference cited here is apparently one leftover from that narrative that somehow got through. Guess I missed it, and so did the Lucasfilm people. And there you have it."
- Star Wars 9 / Star Wars: Episode IX (2019) release date: Dec 20, 2019