In the manga she's the foundress of St. Marie Academy and its branches. She appeared as a ghost to Ichigo and Vanilla in one extra chapter in the manga. The reason of her youthfulness is that since she died, she can manifest herself at any form she wants. She and the Sweets Spirit Queen are both named Marie, in fact, sharing the same name is what started their friendship and eventually gave birth to the whole partnership system between humans and Sweets Spirits.