Carmilla

The protagonist's employer. Lethargic during the day, she does not lack of energy at night. She receives lady callers in the evening, though often these ladies fall asleep while they are here, and the maid must rouse them from their slumber to send them home... and they are always much paler when they leave than they were when they arrived. Someday, she asks her maid to clean her messes after a particularly lively dinner...