The text does not explain why Hapsy does not come to Granny Weatherall’s deathbed, nor does it tell us where Hapsy is. However, toward the end of the story, when Granny asks her daughter Cornelia to "call all the children in," away from what she thinks is a brewing storm, Cornelia replies by saying that "Mother, here we are, all of us." Afterwards, because she is in the throes of death and is quite delirious, Granny thinks that Lydia is Hapsy.

According to Cornelia, all of Granny’s children are assembled at her deathbed. However, Hapsy is not in their midst. This could mean that Hapsy is not within reach—most likely she is already dead. The latter possibility is encouraged by Granny’s own thoughts as she struggles against death. She thinks that she might "see Hapsy again." The text states that "she makes a long journey outward looking for Hapsy" and is worried that she just might not find her. Also, it is worth noting that at the beginning of the story, when Granny is a little stronger, she makes no mention of Hapsy while talking about her children: she says that she is still quite young, since Lydia, John and Cornelia all sought her advice. Later on, she asks Cornelia when Hapsy, George, Lydia, and Jimmy will arrive. She knows that, out of everybody, it is Hapsy that she'd really like to see. As such, Hapsy could have been somebody very dear to her—possibly a daughter or a great friend.

Granny Weatherall has various hallucinations, some of which involve Hapsy. In one, she recalls the time when Hapsy was about to have a baby, and then she immediately sees Hapsy by her bedside in a white cap. In another, she sees Hapsy carrying a baby, and they look at each other before Hapsy "melts from within" and she and the baby disappear into shadows. In yet another, Hapsy whispers to her that "I thought you’d never come, you haven’t changed a bit!"

You have asked a really interesting question as there is a certain ambiguity about the character of Hapsy in this excellent short story. Hapsy is an ambiguous character because her identity and whereabouts are open to interpretation. Her name suggests that she had or has a sunny disposition and that she made or makes Granny Weatherall happy. Note how Hapsy is referred to in the last paragraph:

You'll never see Hapsy again. What about her? "I thought you'd never come." Granny made a long journey outward, looking for Hapsy. What if I don't find her? What then? Her heart sank down and down, there was no bottom to death, she couldn't come to the end of it.

Of course, it is vital to recognise that the stream of consciousness narration means that everything is very confused as Granny Weatherall moves closer and closer to death and makes more and more random connections between her scattered thoughts. And yet it is possible to suggest that Hapsy could be her favourite daughter that she longs to see one more time, or perhaps that Hapsy is a character or a dear friend who is going to welcome Granny Weatherall into the afterlife.

Either way, Hapsy does not appear, and perhaps this is another sign of the rejection of the jilting that Granny Weatherall so courageously faces at the end of the story as she yields herself up to death at the very end.