When Granny thinks about hell, she is thinking about the day she was jilted and the mental anguish she suffers when she thinks about George. She prayed for sixty years trying to forget George, afraid that remembering him would make her lose "her soul in the deep pit of hell".
When Granny thinks about heaven, "she felt easy about her soul. She had her secret comfortable understanding with a few favorite saints who cleared a straight road to God for her. All as surely signed and sealed as the papers for the new forty acres." So Granny thought her place in heaven was guaranteed. She had prayed to her favorite saints who would make sure she would journey straight to heaven to live forever with God.