Amanda Seyfried was 17 in Mean Girls when she played the character 'Karen Smith'.
That was over 19 years ago in 2004.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 37, and has starred in 50 movies in total, 49 of those since Mean Girls was released.
In Mean Girls, I think Amanda Seyfried looks: