Jilly is described as having the same mean smile as her older brother. She appears to wear makeup and her icicle hair is wavier than her brother's stiff upright hair. She wears a spiky dress and cloak with matching shoes.
Like Jack Frost, Jilly has the same hatred towards fairies and is quite close to her brother, saying that no one was better than him. She was thoroughly disliked by the goblins for being too bossy.