Susan worked in films from the age of four. During her acting career as an adult, she specialized in vulnerable, troubled women, and one of her best remembered parts was as Amy in Sam Peckinpah's controversial movie Straw Dogs (1971).
After dating Jack Jones, Andy Gibb, and the Prince of Wales, among others, Susan married the English actor Simon MacCorkindale in 1984.
In 1995 she was chosen by Empire magazine as one of the Hundred Sexiest Stars in Film History. Susan and her husband run a stud farm called Georgian Arabians in Somerset, England. They also have a production company, Amy International, which is named after Susan's role in Straw Dogs.