The grandmother does have a moment of realization, which can be read as a salvation. I concur with the posts above.
When the grandmother identifies with the Misfit and also realizes that she is going to be killed, she has a final humbling. Though she has already admitted some of her mistakes to herself, she does not outwardly recognize her waywardness and her mistakes until she encounters the Misfit, a man more wayward and more falsely righteous than she is.
Yes. In the world of O'Connor's stories, grace is something unexpected, a force outside a person that generates an epiphany. The epiphany and salvation of the grandmother comes in her recognition that she is a sinner just as the Misfit is a sinner:
"Why, you're one of my babies. You're one of my own children!"
In this recognition, the grandmother receives grace as she reaches out to the Misfit. And, after he shoots her, the Misfit himself recognizes her spiritual transformation:
"She would have been a good woman...if it had been someone there to shoot her every minute of her life."
Concerning the Flannery O'Connor short story, "A Good Man is Hard to Find," I believe the grandmother made her way into heaven following her murder by The Misfit. Although her life may have been far from perfect, she was a believer in God and she loved her family. It is true that she deceived the family and caused them to journey down the road that led to their deaths, but she saw the error in her ways at the end and attempted to convert The Misfit. The manner in which she died, on her knees at the hands of a murderous prison escapee, is one that she had little control over.