I see a couple of themes in this story.
Perhaps the main one is race and racism. We see the ways in which the hunter, especially, has absolutely no respect for Phoenix even though she is an elder. This clearly comments on race relations in that time and place.
The other one is responsibility and family. Phoenix is willing to go to all this trouble to get medicine for her grandson because it is her responsiblity as his only family member. In fact, I wonder what is going to happen to him when Phoenix dies, which surely will be in the near future.