Principal began her career in TV commercials, appearing in her first at age 5. After graduating from South Dade Senior High School in 1968, she enrolled at Miami–Dade Community College, intending to study medicine. However, months before completing her first year of studies, she was seriously injured in a car crash while driving home from the library. The other driver was convicted of drunk driving and served jail time. Principal spent months in recovery and was faced with the prospect of having to take her first year of studies over again. After a period of serious introspection, she drastically changed her life by moving to New York City to pursue her acting career, and shortly thereafter to Europe. She studied privately with Jean Scott (professor at the Royal Academy of Dramatic Art) in London, and then in 1971 moved to Los Angeles.