Sarabi hasn't been sleeping well -- not with the famine, not with the hyenas, not with Scar as their king. And so when Nala walks out of the lioness' den, moving like a shadow among the sleepers, Sarabi follows.
The view is desolate, and Nala's expression is bleak and very far-away. Sarabi doesn't want to startle her, so she speaks before she gets close: "You can almost see the shadows of what used to be."
She is speaking of Nala as much as the withered Pridelands.
Nala asks her, "What are we going to do?" and for a moment, Sarabi sees the cub that Nala had been, young and innocent and idealistic in her belief that adults knew how to fix anything. But Nala is grown now (much like Simba would have been, and Sarabi feels a familiar pang of loss at that thought) and so she deserves being treated like an equal.
They speak, and yet much that they want to say remains unspoken: even though they are alone, there is always the possibility of a hyena lurking in the shadows.
Except that then Nala says, flat-out, that she is going to leave the Pridelands and find the scattered herds, and Sarabi feels a kindling of something she hasn't felt since the deaths of Mufasa and Simba.
Nala looks pleadingly at her. "Don't let my mother follow me," she says, and it's less of a child's begging than a request from one equal to another. "Tell her... tell her."
Sarabi reassures her and sends her off, feeling an echo of the hollow loss she felt so many years before. With Simba ... gone, Sarabi had almost considered Nala her daughter (even before that, the two were inseparable, closer than siblings), and now she was losing another member of her family. And Sarafina would be devastated that Nala--
But as Nala slips away, melting into darkness, Sarabi gives herself a shake. It isn't the same as before. Nala isn't dead. Quite the opposite: if she is successful (and she has been successful in the most impossible things, lately) she will bring life back to the pride, to the Pridelands, to her family.
And in the morning, when Sarabi awakens from restless sleep to find Sarafina fretting over Nala not being there, she nuzzles her friend and murmurs that Nala is not missing, Nala has gone to save them, and (in a flash of inspiration that may or may not be truth) that Rafiki knows and is watching over her to make sure that no harm comes to her.
Sarafina relaxes only a bit. "Where has she gone?"
"To find hope," Sarabi answers. "To find life."
Sarafina paces. "What can I do to help her?"
"Wait," Sarabi says. "Endure. Believe."
It is all they can do.