She is the timid and shy younger sister of Esty Dee. She is easily intimidated by people who are scary looking or have serious personalities, like Rufus, Sterk, Cordelia and even Mimi. She has a distinct interest in forbidden love, especially girl on girl relationships and often fantasies scenarios out loud, much to the chagrin of those within earshot.
It is unknown as to what Filly's true sexual preference is, but she does talk about meeting a handsome prince and getting involved in a forbidden relationship with him. When she's not working, she spends most of her time fantasizing and day dreaming.
She first appears in Atelier Totori when she takes on the role of receptionist for the adventurer's guild after her sister leaves her job to go search for a husband. She has been left in charge of distributing quests and rewards to adventurers, but has trouble doing so because she is terrified of anyone scary looking.
She is able to work well with Totori however because she has no fear of cute, young girls. Although she struggles at times to perform at her job, she tries her best, knowing that her sister's reputation is on the line if she does poorly.
She gives out several monster hunting and material quests to Meruru from the town's tavern, and closely helps to monitor Meruru's progress throughout the years.
- In the manual for Atelier Arland DX, her name is listed as Filly Airhart, closer to the original Erhard Japanese name. This appears to be a translation issue as later games featuring her sister utilize the Dee last name.
- Filly is the term for a young female horse, as she is Esty's younger nervous sister