Fairy-Ham has a very important job in both of her forms: To keep Ham-Ham Land running smoothly during the day and making sure everyone is happy. She is shown to be playful in her hamster form, but she is much more serious when she turns into a human spirit.
She seems to have a close relationship with the night keeper of the park, Devil-Ham. She chides him for his bad habits (licking his paws) and even got upset with him when he didn't ask her on a "date".
See also: Fairy-Ham/Gallery