Hiram and Bobby Lee returned from the woods and stood over the ditch, looking down at the grandmother who half sat and half lay in a puddle of blood with her legs crossed under her like a child's and her face smiling up at the cloudless sky. (137)
This last description of the grandmother does seem strangely hopeful. She's smiling, and though she's lying in a bloody heap on the ground, her legs are described as "like a child's," as if in this last moment she's regained the innocence of a child (although the two actual children in the book didn't exactly have a whole lot of that). This could suggest that the moment of grace is in fact real; the grandmother has, in some way, "resolved" her life happily. Though if you don't buy that, you could also say that she died with a faked smile on her lips.