Countess Rose was an English aristocrat who ran "Princess Seminars" for girls who wanted to learn etiquette and manners. She was turned into the Youma Shakoukai by Kunzite, and attempted to lure Sailor Moon to her Princess Seminars in order to discover her identity. She did manage to pinpoint Usagi as possibly being Sailor Moon, but she was healed by Moon Healing Escalation and forgot her time as a Youma before she could tell Kunzite.
(Source: Project WikiMoon)