Leias' memories of her mother
In ROTJ Leia descrides her memories of her mother to Luke as being "very beautiful, but sad" . I was thinking that she must be talking about her mother on Alderan, Bails wife. The way Bail says to Yoda and Ob1 ' My wife and I will take the girl, we've always wanted to adopt a baby girl" . So maybe the sadness that Leia felt had something to do with her ( alderaan) mother inability to have childeren and her knowledge of tragic curcumstances that lead to her adopting Leia.
I think most people think that in ROTJ Leia is talking about Padme.