Over-moralising about fiction is kinda silly. Things that would be red flags in real life can be nice manga, as long as we're aware of what we're reading and don't base our understanding of the real world on it.
That being said, several people have mentioned how it doesn't count as immoral because you can guess that the maid secretly wanted it based on her expression, and I wanted to say that this is mega cringe and I sure hope that's not how you approach real life.