In As I Lay Dying, the case could be made that almost any of the Bundrens is a hero in the sense that they undergo a hero's journey, including, I believe, Addie. Her journey involves her death.
The first step of the hero's journey is existing in the ordinary world, which, for Addie, means living. Next, she must be called to death, which her father does. As she recalls, her father told her that living is to prepare for being dead for a long time. Her refusal is not an outright refusal; rather, she spends significant time unsure of how best to prepare to be dead, and assumes that hitting children is the way to do it. She finally accepts her call to prepare for death when she has Darl and decides to take revenge on Anse by making him take her to Jefferson when she dies. She mentions that that was when she realized that her father had been right, even if he couldn't have known it. This is both an acceptance and a modification of her quest: she accepts that she should prepare for death by deciding to use her death to hurt Anse. After she has Jewel and two other children, she feels that she can get ready to die, and then she does.
After she dies, Addie makes Anse's journey less enjoyable and more difficult by stinking quite badly, perhaps making bacteria her ally, but I feel that she does considerably more than that. It is my (outlandish) interpretation that Addie may have influence from beyond the grave, which she uses to produce the storm which floods the river Anse has to cross and causes the wave of inconveniences which follow. This ability is hinted at in the last two paragraphs of Addie's narration, where she says that she could get ready to die after she had implied that she had lived much of her life trying to prepare for death. She may have meant that she was plotting Anse's problems. In the final paragraph, she mentions that, to people like Cora, sin and salvation are just words. Contrasting this to her statement that "words are no good" implies that she wants to use more than words; she prepares events for Anse's displeasure.
If she indeed causes problems for Anse after death, then her ability to do so would be the supernatural aid of her hero's journey. The problem is that, though she may find personal pleasure in taking revenge from beyond the grave, Addie never seems to complete her heroic journey. Though her literal travels end, Anse's suffering ends with it. Perhaps she is content at this point, and her return to the ordinary world is simply being buried.
