I spoke with her sister Linda Patrick Thiem, and obtained information on her death. It seems that Ann (Maureen in the yearbook) had some knee surgery. Shortly after that, she bumped her knee and hurt it. The doctor gave her some medicine. That night, she became sick and died. It may have been a blood clot.
She died March 23, 2000 and is buried in Columbus, Nebraska.
Background: She, Linda and their family moved to Arkansas and they graduated there.