Christina Applegate was 43 in Alvin and the Chipmunks: The Road Chip when she played the character 'Brittany (voice)'.
That was over 8 years ago in 2015.
Today she is 52, and has starred in 50 movies in total, 4 of those since Alvin and the Chipmunks: The Road Chip was released.
In Alvin and the Chipmunks: The Road Chip, I think Christina Applegate looks: