"Oh, Luke..." she breathed softly. His question was a hard one for Padmé to hear asked. Or, rather, a hard one to hear answered. She loved her daughter just as much as she loved her son, but clearly Leia didn't have the same sense of longing for parents that Luke - even grown - possessed.
Of course, Luke had been raised by a man who had apparently beaten him for using abilities he'd had no way of understanding or controling. Leia, meanwhile, had been raised by Bail Organa. One of the most noble, understanding men that Padmé had ever had the pleasure of calling a friend.
The startling differences in her children's childhoods only caused her to feel yet more guilt for not having been there for them as a mother should have. She was trying to ammend that mistake when it came to Luke, now that she'd been given the chance. With Leia, however, she feared it was simply too late.