Cornell graduated from Rollins College in Winter Park, Florida in 1986. She made small guest appearances on two television series: Gabriel's Fire and Thirtysomething, as well as several made-for-TV movies. Then she appeared in the 1988 comedy film Married to the Mob, but her most famous and first starring role came shortly afterwards in the horror film hits Halloween 4: The Return of Michael Myers and Halloween 5: The Revenge of Michael Myers as Rachel Carruthers.
She eventually rejoined the industry as an executive producer of 1999's Free Enterprise and 2000's The Specials. (She also had acting roles in each of those films.) In 2003, she returned to her horror roots by appearing in House of the Dead.