That wasn't strictly true. While Luna was occasionally quite blunt, she was never really entirely tactless. Sensitive subjects were more her particular specialty, and while she quite often said what other people wouldn't even think of saying, it was usually to bring up or drive home a point that was otherwise being missed. In this situation, though, he was quite correct. She was simply stating facts; why wouldn't observations about a room be socially acceptable?
As to her request, that was possibly a little more tender of a subject, but there wasn't anyone else she could ask. "Might I have a little more water?" she asked, tilting her head slightly to one side. She had the basics for hygiene, and Argus took care of the disposal issue magically, since her own wand had been taken, but... "It is rather difficult to wash with only a pitcher-full, though I've been doing the best I can."