I really thought this scene was touching. Rei has been to hell and back. She lost everything as a child and was raised by a diabolical mass murderer. Her childhood identity was stripped away and her whole life she was taught how cruel and hopeless the world is. Satsuki doesn’t judge her at all, though. She admits that there’s no way she could understand how Rei feels and doesn’t at all deny Rei’s experience. Satsuki acknowledges that Rei has the power to help and educate people. Rei’s unique experience can help her change the world for the better in a way that no one else’s can.