You will find different interpretations regarding the ending of O'Connor's story. I tend to think that the grandmother has changed in a genuine manner. From where she was at the start of the story to where she has come, O'Connor's text reflects a transformation. Granted, that this could be due to the fact that she has a gun in her face. However, I think that O'Connor's redemptive and restorative theme is so powerfully compelling that the intent and motivation is almost secondary to the condition of change that is evident.
When the story begins, one almost can imagine needing to take drastic action simply to keep her to stop talking. She is incessant on "her way" and does whatever she needs to in order to ensure it. Her insistence on calling her son, "Boy" even though it is evident that he has his own family and has established himself as an independent man is reflective of how the grandmother sees her way as the only way. Such denigrating language is seen in the "pickaninny" comment regarding children of color. The grandmother's disrespect of her daughter in law is also a critical aspect of her characterization. Her reveries about the past are not made as part of social reflection. Rather, they are done to reflect a time where she had power. She manipulates the children in order to get "her way." The mere notion of "a good man is hard to find" is a statement on how the grandmother believes that her notion of the good is the absolutist interpretation of reality. This is limited in its scope because it sees contextual reality as the only notion of the good. The grandmother exemplifies this in her initial frame of reference
The transformation which takes place at the end of the narrative speaks a redemptive element found within the grandmother. The insistence on her absolutist interpretation of reality ends when she says, "You're The Misfit!...I recognized you at once!" It is the last moment in which she speaks of a temporal world, a design where she interrupts his son while he trays to navigate he and his family from a challenging situation. It is the last moment in which she speaks with a triviality to her, as if recognizing the criminal is going to net her acknowledgement. In other words, when she speaks of the looming danger, it is an implicit understanding that the situation is bigger than she and her own vision of the world. It necessitates a different frame of reference in order to appropriate it. Contingent is shown to give way to transcendent.
Through this, the transformation begins. It is at this point in the narrative where the desperation that brings about change is evident. This becomes evident from the start of her dialogue with the criminal, as seen when she initially pleads with him: "I know you're a good man. You don't look a bit like you have common blood. I know you must come from nice people!" In this, one sees flickers of her past world view of temporal judgment ("common blood" and "nice people"), but there is also the reaching out to a transcendental notion of the good which will replace the grandmother's limited view of being in the world. In appealing to his "good" nature, the grandmother moves into a transcendental notion of acceptance when she speaks of what exists in "his heart." This appeal to something larger than contextual reality is evident in the grandmother's plea to the criminal about the idea of a "better life:" ""You could be honest too if you'd only try," said the grandmother. "Think how wonderful it would be to settle down and live a comfortable life and not have to think about somebody chasing you all the time." Whether she is seeking to extricate herself through conversation might not be as important as how the grandmother is reaching towards a vision that is transcendentally good. It is a vision in which the ideas of "settling down" and seeking to "live a comfortable life" articulate elements of what it means to be a human being. In these statements, the grandmother's language and verbal frame of reference have changed from embracing trivial and contingent notions of the good to aspiring to something more definable in terms of what it means to live in the modern setting.
When the grandmother turns to prayer, it helps to accelerate the eventual transformation that will define her character. Her insistence on prayer for herself and the criminal reflect this. In her desperation for prayer, she reverts back to her old ways of thought, thinking that offering her entire sum of money will help her. It is with that the grandmother evolves, thinking about her son with the lament ladened cry of "Bailey Boy." Her claim of Jesus perhaps not "raising the dead" illuminates her fading belief in external salvation, setting the stage for her own reclamation and transformation. This process culminates in the statement of grace that becomes the essence of the grandmother's change:
His voice seemed about to crack and the grandmother's head cleared for an instant. She saw the man's face twisted close to her own as if he were going to cry and she murmured, "Why you're one of my babies. You're one of my own children !" She reached out and touched him on the shoulder. The Misfit sprang back as if a snake had bitten him and shot her three times through the chest. Then he put his gun down on the ground and took off his glasses and began to clean them.
The grandmother becomes a universal face of love and divine grace. She speaks to this with the appropriation of the criminal as one of her own. Her last words being one of deified grace, following a spiritually transcendent view of the world. It is here in which she has changed. Consider the lexical frame of reference she used to use and that which is spoken at the end to reflect the full effect of this change. Even her physicality speaks to this change, as O'Connor describes her body as residing "in a puddle of blood with her legs crossed under her like a child's and her face smiling up at the cloudless sky." It is here in which the grandmother's transformation is complete. She has become the change she envisioned when she first found herself in danger. The grandmother might have said what she said to live. Yet, there is an absolute sense of change when she invokes divine transcendence through personal appropriation in her last words.