Campbell is from Hinsdale, Illinois. Her parents are Georganne and John Campbell, and she has a younger brother, Johnny. She was discovered in a hair salon in Chicago at the age of 10. And her first big break was as a guest star on Prison Break, appearing in five episodes. She also appeared in a nationwide commercial for Build-A-Bear Workshop and played the character of Darla in the 2008 movie The Poker House. In 2010, she appeared in the Disney Channel television series Zeke and Luther, portraying Dani before starring in the television movie StarStruck in the same year. Upon StarStruck's release, she had signed a development deal with the company. She starred in the movie Prom, released on April 29, 2011, co-starring with Nicholas Braun, Nolan Sotillo and Aimee Teegarden. In 2013, she received a starring role in the television series The Originals, where she portrays the role of a powerful, sixteen-year-old witch named Davina. In late 2013, Campbell was announced to star in the 2014 film 16 South, alongside Luke Benward.