Heather Burns was 21 in You've Got Mail when she played the character 'Christina Plutzker'.
That was over 26 years ago in 1998.
This was her first recorded movie acting credit (although may not technically be her first actual acting role).
Today she is 49, and has starred in 21 movies in total, 20 of those since You've Got Mail was released.
In You've Got Mail, I think Heather Burns looks: