I'm watching ROTJ now and Leia just said she remembers her mother by images and feelings. -Images that could have been shown to her of Padme by her adoptive parents. She may not have been told who exactly her mother was (so she wouldn't discover that she was married to Vader and he is her father). But images and such are probable. As her adoptive parents would want her to know of her real mother. -Feelings, who knows. Maybe since the force is in Leia as well, she could have gotten things passed down from Anakin and Padme that give her a sort of connection to her parents. Or at least her mother. NOT Vader. Or she just remembers her mom from stories told to her by people who knew her and that's why. I dunno. Like had no idea who his parents were. I'm led to believe Lies was at least told some details about her parents. Just not big details that would jepordize her life.