Had she simply said that, he would have pulled away. But she keeps him from it, holding his hand in place and leaving him as confused as she is, and also as conflicted. He can feel that simultaneous pull and push from her and he doesn't know how to respond to either.

He wonders what he would want, in her position, and flashes of memory rise in answer. Snoke, a year in the past, wiping a tear from his face and berating its existence. And Vader, only a few days ago, watching tears well in his eyes and making no comment at all on it at all save for a comforting hand on his shoulder.

He doesn't understand what this is. He's not sure whether he can forgive her for her betrayals, and he's sure she likewise hasn't forgiven him. But for right at this moment, he finds himself very quietly saying, "It's okay. You can cry."