Jill Hennessy was 18 in Dead Ringers when she played the character 'Mimsy'.
That was over 36 years ago in 1988.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 55, and has starred in 34 movies in total, 33 of those since Dead Ringers was released.
In Dead Ringers, I think Jill Hennessy looks: