"Maybe." There are very few ways to easily kill a vampire, and she's trusting Corwin with a main one, in a way - yes, she locks the door to her room during the day, but she doesn't have illusions regarding that he could get into that room and draw open the curtains any time if he wanted. But she trusts him, is the point, and that is just another reason to monitor this closely, lest he come under the influence of someone who wants to harm her. "And maybe they can harm you, too."