Narcissa did not see Meaghan's expression, but would have had plenty to say if she had. Firstly, house-elves weren't human so it honestly didn't matter how one treated them. And secondly, Dobby had proved his incompetence enough at this point to deserve it.
She smiled as though Meaghan had made an incredibly amusing remark, in reality fighting a yawn. "I would imagine not. But there must be some benefits, am I correct? Do you enjoy the publicity?"