Gillian has shoulder-length blonde hair and green eyes. She wears a knit cap covered in pins. She has more handmade pins on her coat.
Gillian is a cheerful and optimistic individual and acts happy around her fellow resistance members. She values the lives of her allies to the degree of risking her own, noticeably her senior Lucas, as she told Nigel to sacrifice her life to keep Lucas safe.
Ever since she was shipped from Grand Valley, Gillian started to discover the true horrors of living in Goldy Pond, watching as her sister and countless other orphans were hunted to their deaths by the demons. From then on, she developed a vengeful, ruthless side of her personality that she put on display during the resistance. This let her fight and kill demons like Luce without hesitation.
Upon meeting Emma, Oliver introduced her to the members of the Goldy Pond Resistance. Gillian cheerfully introduced herself to Emma and showed Emma her Farm Identifier code that was implemented right below the center of her collarbone.
She recalled how her sister was killed, and went on to kill Luce's attendants and Luce himself. Later, she is wounded due to a surprise attack from Bayon, rescued by Pepe and Nigel, and taken back to where Lucas and the younger kids are hiding out to receive medical care.
- The following are Gillian's rankings in some of The Promised Neverland's official popularity polls.
- Her pins copy her expressions. For example, if she's shocked, her pins will look shocked as well.
- She made all her pins by hand.
- She also made the little clowns seen throughout Goldy Pond.