Linda Blair was 17 in Exorcist II: The Heretic when she played the character 'Regan MacNeil'.
That was over 47 years ago in 1977.
Today she is 65, and has starred in 65 movies in total, 55 of those since Exorcist II: The Heretic was released.
In Exorcist II: The Heretic, I think Linda Blair looks: