The author of the well-known Sisterhood of the Travelling Pants stories. And many other very good young adult novels that feature coming of age.

The Sisterhood of the Traveling Pants by Ann Brashares (Sisterhood #1)
The Second Summer of the Sisterhood by Ann Brashares (Sisterhood #2)
Girls in Pants by Ann Brashares (Sisterhood #3)
Forever in Blue by Ann Brashares (Sisterhood #4)
Sisterhood Everlasting by Ann Brashares (Sisterhood #5)