"My long-time client and friend Billie Letts passed away this morning at St. Francis hospital. We are all devastated," Johnson said Saturday evening. 

Letts was nationally known for her works including "Where The Heart Is," which was made into a movie staring Natalie Portman and Ashley Judd. She was also the mother of Pulitzer prize-winning Tulsa native Tracy Letts, author of "August: Osage County." That screenplay and film were based on his mother's dysfunctional family.

In addition to her writing career, Billie Letts was an educator who taught at Southeastern Oklahoma State University.

Letts' husband Dennis, who performed in the stage version of "August: Osage County," preceded her in death in 2008. She had two other children, musician and composer Shawn Letts and Dana Letts.