Gemma is the daughter of high school history teacher and football coach Greg Grier and physician Heidi Grier and the older sister of Ollie Grier. She is introduced as a fashionable yet friendly dancer, best friends with Skye Park, and the girlfriend of her childhood friend, Micah Kelley. Gemma remains supportive of Micah, who is a second-string receiver on the high school football team coached by her father.