Ferguson was born in Hacienda Heights, California. She is the daughter of devout Roman Catholic school teachers Theresa Ann (née Gore) and Jon Patrick Ferguson. Her ancestry includes Irish, Scottish, English, Mexican (from a great-grandmother) and Native American. She was raised Roman Catholic. She attended Mesa Robles Middle School and Glen A. Wilson High School. She was a cheerleader, straight-A student and spelling bee champion, as well as a Girl Scout.