I know that he can't kill human after being without their company for years, but, just kill her dude, you said it yourself she killed a lot of dumbass who where following her, the betraying is so clear even a blind can see it...~
I doubt the MC is going to trust the bitch for a single moment. However, it's difficult for him to leave her behind because of his buddy. The sidekick dude doesn't know Churou is a traitor by nature, so the poor kid is simping for her. I imagine the MC is merely calculating Churou will get herself killed before long, and that's it. His friend can't blame him for that.