Is this Hotaru cosplaying as Aori or did the artist mistype?

JHDX said:

Is this Hotaru cosplaying as Aori or did the artist mistype?

Yeah, I was thrown off by that. Perhaps I mistranslated it?

ホタルちゃん = Hotaru-chan
専属 = exclusive; attached to; specialist;
執事 = (1) steward; butler; (2) court official; (3) deacon (Anglican, Lutheran, etc.)
です = is
が = but/though
なに = what
か = Makes the sentence a question.

So maybe it's "It's the butler attached to Hotaru-chan, although what?" ... IDK... ???