[Technically, she's helping him with his dare. That's a very nice thing to do. Also she's just fine with Sebastian being the one person in Kiseki who doesn't know her name for the time being. So good to know they're on the same page.]
Oh, not at all! I'm sure keeping a house clean all the time must be difficult. [Maybe Sebastian just isn't up to it? No, she doesn't mean that at all, but all the same.]