The death of Native culture
There are many thematic reminders of the tragic death of Native American culture. There is the whipping at school, corporal punishment for speaking her native language instead of struggling to speak English, which she hates. The grandmother is a symbol for her culture, and her crippling arthritis is also an indication of powerlessness to fight against time and death.
Isolation and boredom
For the girl, names aren't really that important. She doesn't like speaking English, so mostly she stays perfectly isolated, barely talking to others, occasionally talking to a jailer or something. She is bored, which is obvious from her flashbacks, flashbacks about boredom indeed. She remembers leaving her grandmother behind to go be with someone new, and then leaving him behind too.
Death and mortality
At the end of the novel, the old man narrator gives way to death and faces it. He describes the moment of looking death in its eyes, so to speak. This is a nice ending to the deathly dirges of the novel's plot. The girl is riddled by death. Her grandmother is dying, her would-be caretaker dies, and her parents are killed by the person she "murders" by luring him to his death, walking out to the ice where she knew he would fall through and die.
