Filla hasn't shown up in the books, but her brother Fillo has. She's mentioned in The Wolf's Pawn. Filla is the iconic for a prestige class in Terah-the vagabond tyrant. It's a gnome barbarian basically, something that the publisher's son thought was pretty funny. (I think it's funny too.)

Take note of her sword. Gnomes think minor pain in others is funny, but the restriction is, it can't be more than what is caused by a number nine needle. This is Filla's take on what a number nine needle is and since it's open to debate on what that means, no one is arguing with her.