Fans have debated on this for some time, and right now the current major theory is that Leia is incorrectly remembering Padme’s body double Sabé, who was a part of the rebellion and worked with Bail Organa.
The scene made Leia’s comments in Return of the Jedi confusing in which she talked about having memories of Padme Amidala.
Star Wars: Revenge Of The Sith statement a claim from Leia, who claims to remember her mother despite us knowing she died of a broken heart during childbirth.
Another idea is that Leia was accidentally channeling her Force sensitivity to see Padme, which is another cool explanation.