Petty graduated from North High School in Sioux City, Iowa in 1982 and worked for several years in Omaha as a graphic designer before pursuing acting.
The role that made Petty famous was playing Keanu Reeves' surfer girlfriend in the 1991 action thriller Point Break. Previous to that, she got her break starring with Richard Grieco in Fox's Booker. In 1992, Petty was featured as 'Kit' in the box office hit A League of Their Own which starred Tom Hanks and Madonna. Petty gained a starring role in Tank Girl in 1994, which made her into a cult icon. Her other films include Free Willy and In The Army Now. She also co-starred on a short-lived television series called Lush Life with her friend Karyn Parsons. Petty has also made marks in voicing "Livewire" on Warner Bros., The Animated Series, and Batman.