Cassidy was discovered at age 14 by a talent agent in Florida and started modeling and acting in commercials. She got a one year scholarship at the Huntington Film Institute in Orlando, which led to a part in the Nickelodeon series Clarissa Explains It All. She then (1993) moved to Los Angeles together with her mother Amy to start an acting career. Her first on-screen appearance was in the TV show Angel Falls; next she was cast in the short-lived Spelling show Models Inc..
Proposed by and engaged to a medical student on Thanksgiving Day 1999 during the Macy's Thanksgiving Parade. Has a brother named Cody and a sister named Dustin. Her dog is a Bouveau named Louise. Retired from acting so she could enjoy her marriage and soon have children.