Nikolai would be very annoyed if Nina made herself sick, but she seemed to visit cemeteries and he was one of the people who watched her back. Plus, she had spread a cold which seemed to allow her some breathing room.
The war was something no one needed. And he'd keep fighting for the good of his people, for his country, for a safe place for Grisha.
"I think it's hard enough for people to understand a Heartrender, but a Corpsewitch? And you know Kaz. He never wants people to have information he does. Though, I do find it interesting that she's chosen to live with someone else."