She is strict.
When Dracula left for the vampire council on official vampire business he called upon his older sister, Lydia, to look after and run the hotel in his absence. Lydia agreed and decided to use this opportunity to bring more tradition and order into the hotel.
Upon arrival Lydia immediately began her work in running the Hotel with her pet chicken Diane. She is constantly annoyed with her niece Mavis breaking things and causing a mess. Much like other Monsters she hates Humans.
Despite being constantly aggravated by Mavis and her friends, she is secretly proud of her niece and the work she does at the hotel.