She had thought of this, back when he was cutting his steak with that knife. Thought of him using it on his victims, then thought of him using it on her, the same way he enjoyed choking her when he fucked her, getting that thrill of having her life in his hands. This was more terrifying than his hands around her throat, though. He was sufficiently skilled with that knife that he could kill her in an instant, whereas strangling her took time, time during which she could fight back. And this was much closer to how he murdered his victims.

If he had asked her about knifeplay beforehand, she would have said no.

She's already breathing a little roughly with arousal and fear when he guides his cock to her entrance. When he thrusts inside her she groans desperately, her eyelids fluttering for a moment at the sensation.

He loved her. He did. There was no reason for him to kill her. She knew this. And she wanted to be able to offer herself to him completely, even now, but she couldn't yet. She still watched him, trying to think of ways to defend herself.