Thelma I. "Bonnie" Zimmermann, of St. Peters, Missouri, died on Friday, February 24, 2012 at the age of 84. She was the loving wife of Walt Zimmermann; beloved daughter of the late William and Clara Kohlschreiber; devoted mother of Constance Lynn Istwan, Sharon Leigh (Michael) McAllister, and Gary K. (Shelby) Zimmermann; cherished grandmother of Matthew, Michelle, Angela, Andrew, Jennifer, Cristin, Douglas, Jacob, Susan, and Steven; treasured great-grandmother of Avery, Finley, Joseph, Leanna, Zachary, Megan, Kathy, Kylee, and DJ. She is preceded in death by a daughter, Kathy Marie Hartman; three sisters, Clara, Margaret, and Irma; and one brother, William. Thelma was a longtime member of Chapel of the Cross Lutheran Church in St. Peters. Memorials may be made to Memorials may be made to the American Diabetes Association or Chapel of the Cross Lutheran Church.