[That...that is unacceptable. Even for a child. Perhaps especially for a child. Even if it's a truth that won't matter much on the open sea of their home, it's a truth nontheless. So Robin will go to Vivi's door and put a hand on it but not come in]

It's the truth. Calling someone a liar just because you can't accept it is immaturity on your part. You won't remember. That is just the way it is.