Before the Sudden DepartureEdit
In stark contrast to her somber personality later in the show's chronology, Jill was a happy, young teenager.
After the Sudden DepartureEdit
After the events of October 14 and for the duration of most of the series Jill is disillusioned. Though no members of her own family depart on the 14th Jill troubles to cope in the post departure world as she witnesses what structure she has in her life dissipate. With her mother Laurie a part of the Guilty Remnant, and half brother Tommy MIA, Jill's only support is her father chief Kevin Garvey and her best friend Aimee. Initially Jill seems to make trouble for troubles sake, yet as the story progresses, Jill begins to show more method in her actions. By the series one finally Jill has begun to trust her father and becomes very optimistic for her developing family's future come season 2.
Jill is one of the few characters explicitly said to have witnessed a departure. In the novel it is her best friend Jen with whom she is on the couch watching youtube, in the show it is an unidentified student at the science fair who ends the circuit excitement Jill and Tommy participate in.
In the novel Jill's hair is suggested to be very short as a result of her rebelliously shaving her head, whereas throughout the show her hair is long.