Seeing the challenge for what it was, Toby glanced between them, before giving Chris a dry smirk. "Is that a party for two, or three?" Surprisingly, she wasn't so much worried about some concept of fidelity- that would imply she thought of what they had as some sort of monogamous relationship, which she wasn't crazy enough to assume to ask from Chris.
Her concern was more for the detective himself, and what might happen to him if he didn't watch his step around Chris. Toby had the leeway of the man loving her, and she still worried for her own safety, on occasion. Of course she would worry for a stranger- even if he happened to have Chris' face. Still, she wouldn't demand to watch, knowing Chris wouldn't allow it just to spite her.