Hayley first appeared in national commercials for GM, On Star, K-Mart, and Slim Jim, and became the TV spokesperson for Cinnamon Toast Crunch. In addition, she had a couple of guest star roles on Nickelodeon's Unfabulous (2004). As a dancer, she studied with Scotty Nyugen. She is a prolific songwriter and she plays the drums, keyboards, and guitar. She was a member of a five girl-singing group, the Stunners up until their disbandment in 2011. The Stunners have released their first five-song EP with the video "Dancing Around the Truth." Scooby-Doo! The Mystery Begins (2009) debuted on Cartoon Network in 2009 with Hayley in the iconic role of Velma Dinkley. She appeared in the role of Stevie on Disney Channel's Wizards of Waverly Place (2007). Hayley, with the Stunners, toured as Justin Bieber's opening act in the summer of 2010.

Hayley recently joined the cast of the new CBS mid-season drama CSI: Cyber (2015). The series revolves around Special Agent Avery Ryan (Patricia Arquette), who is in charge of the Cyber Crime Division at Quantico, Virginia. Hayley plays Raven, a rookie techie working in the division who is an expert in social media, cyber trends, and international relations.

This past summer, Hayley filmed the Universal feature Jem and the Holograms (2015), in which she plays Aja. This Jon M. Chu-helmed film is set to be released on October 23, 2015. She followed that with Insidious: Chapter 3 (2015), the third installment in the successful franchise. Hayley can also be seen in the recurring role of Gabi, an ex-cyberbully in an all-girl group home on the breakout ABC Family show The Fosters (2013). Prior to this, she guest-starred on the hit CW series The Vampire Diaries (2009) and also appeared in the Disney Channel original movie Lemonade Mouth (2011).

In addition to a successful acting career, Hayley is a prolific songwriter and gifted musician. To follow up her solo artist debut in 2013, she is scheduled to release her new EP, "This Side of Paradise," in 2015. Working in collaboration with producer James Flannigan, she recorded the new album in London as well as in a makeshift studio in the garage of her Los Angeles home. Her music has garnered praise in multiple online publications including Nylon, Just Jared, Earmilk, and Hype Machine.