I think I’ve read that George said that Leia was supposed to go and live with her real mother for 2 years before she died.

Edit: here is the bit I was thinking of:

Lucas: Leia and Luke’s mother go to Alderaan and are taken in by the king there, who is a friend of Ben’s. She dies shortly thereafter and Leia is brought up by her foster parents. She knows that her real mother died.

Kasdan: She does know that?

Lucas: Yes, so we can bring that out when Luke is talking to her; she can say that her mother died when “I was two years old.”