I really like this dynamics of this moment. Dr. Oosterhuis needed Marina/Uncia to have any hope at all, and despite how she realizes her colossal error, she still needs him, too.
So at the moment he most wants to give up, she won’t let him. She still believes his brilliance can be re-purposed for good. Perhaps she even still cares about him; he’s certainly a masterful manipulator of impressionable teenagers.
The end of this chapter will bring closure to this arc, and set the stage for what comes next. Stay tuned!