This does not appear to be an applicable analogy here. If it were, Mom (presumably the owner of the house) would not be able to identify anybody in the house, only how many people there are in total in the house. Not something she'd be happy with, I assume, nor you. (Strangers? Friends? Family?) And your complaint appears to be that you didn't have ownership rights in your room -- but if you had had them, according to your version of privacy, you could only tell that there was one other person in the room with you, but not that it was Mabel. It could have been her dad. Presumably also not what you would have wanted.