The probability that Draco was in her room asking her that question just so he could pass along what he learned to Rodolphus was quite high. She was nervous to answer, nervous that saying the wrong thing would put Rodolphus on the defensive. In order to learn what she needed to learn, she had to keep him believing that she trusted him. Or at the very least that she didn't distrust him. Refusing to answer would be suspicious. She might have to start at the very beginning with earning her host's trust. But, she also would be in trouble if she admitted the truth. She'd been afraid that night because of what the Lestrange brothers did to her. If it got back to either one of them that she was more aware of what happened that night than they knew, she would be in grave danger. Rodolphus might decide that it would be better to just use another body, whatever that meant. A believable lie would have to do.