Alyson Stoner was 16 in Phineas and Ferb: The Movie: Across the 2nd Dimension when she played the character 'Isabella Garcia-Shapiro / Isabella-2 (voice)'.
That was over 12 years ago in 2011.
Today she is 30, and has starred in 35 movies in total, 19 of those since Phineas and Ferb: The Movie: Across the 2nd Dimension was released.
In Phineas and Ferb: The Movie: Across the 2nd Dimension, I think Alyson Stoner looks: