Debi Derryberry was 39 in Horton Hears a Who! when she played the character 'Who Mom / Additional Voices (voice)'.
That was over 16 years ago in 2008.
Today she is 56, and has starred in 87 movies in total, 34 of those since Horton Hears a Who! was released.
In Horton Hears a Who!, I think Debi Derryberry looks: