Marcia Gay Harden was 18 in Not Only Strangers when she played an uncredited character.
That was over 45 years ago in 1979.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 64, and has starred in 87 movies in total, 86 of those since Not Only Strangers was released.
In Not Only Strangers, I think Marcia Gay Harden looks: