I actually agree with Jedidz23's opinion on how Leia can remember her mother though it seems impossible... I view it as a force thing mostly. Potentially a difference in the way the two children are raised, or things they're told during childhood, form the visions they have through the force...
But to me the explanation that first came to my mind (and which I offered my buddy tonight who surprisingly cited the Leia flaw right away, he impressed me being a more casual fan

) was that Leia's having sort of "dreams" she perceives as reality/memory of her mother... I don't take that as grasping at straws since my mind didn't even stretch to come up with an excuse, but rather that came right to me when my buddy asked about that. Why Luke doesn't have a memory... I suppose anything from the focus of his thoughts to the focus of his life in general could've had an effect on that. Luke only asks about their mother after he's seemingly had some time to reflect on who he was told his father was... Maybe Luke's lack of thought towards his family (since his Uncle had put something else in his mind) made him lose memory of her? Lose the connection that Leia perhaps retains because maybe Bail/wife raised her with more talk of Padme... Who knows.
It's one of those loose-ends I'm sorta sad that the movie didn't tie off... That, the Qui-Gon thing, etc... There definitely was room for another hour's worth of footage. I feel that way about very little around the prequals. ROTS really won me.
The classic trilogy had me wanting more... AOTC only had me wanting more about the war, maybe a tie-in space battle (Such a missing aspect of these 3 films), but ROTS I could've sat through another hour of just MORE.

After 3 screenings I'm set for a 4th with anticipation. Just hearing my buddies walk out with me tonight (Casual fans, but not die-hards who have to be at premieres or collect anything) and they're raving about the movie... That felt great. Guys that usually were critical of the films were now asking me questions, and actually discussing stuff with me without making fun of SW in its current state. That rocked.