It was revealed that Hershel's wife was a great mother, religious and all. Hershel saw her get bit and did not have the heart to kill her. She was killed as a walker by one of Rick's group following Shane's orders to execute all walkers in the barn, alongside Hershel's walker oldest son.In the comics, the same thing happened in background but Hershel's walker wife was killed by Rick as he returned to Hershel's farm after the Governor's second raid on the prison.