Betsy studied English at the University of North Carolina, Chapel Hill from 1973 to 1977 and acting at the Central School of Speech and Drama in the United Kingdom from 1977 to 1980. She was discovered there, filming a movie with Sean Connery titled Five Days One Summer (1982). Like Five Days One Summer, most of her films are based in Europe. Her most famous role, perhaps, is her portrayal of Neely Pritt in Shock Treatment (1981). She also played alongside Pierce Brosnan and Michael Caine in the film version of The Fourth Protocol (1987) and enjoyed a cameo in the Ashley Judd movie Double Jeopardy (1999). Brantley was also the performance model for Jessica Rabbit in Who Framed Roger Rabbit (1988).
She has also appeared as Elsie Cubitt in the Granada Television production of The Dancing Men, from The Adventures of Sherlock Holmes by Sir Arthur Conan Doyle, and also appeared in the 1987 BBC Horizon film, Life Story (the story of the discovery of the DNA double helix) as James Watson's sister, Elizabeth Watson.
Brantley played Dolph Lundgren's girlfriend in Dark Angel (1990, retitled I Come in Peace in America).
