Lara Flynn Boyle was 17 in Poltergeist III when she played the character 'Donna Gardner'.
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 54, and has starred in 46 movies in total, 45 of those since Poltergeist III was released.
In Poltergeist III, I think Lara Flynn Boyle looks: