Do you think the moment when the water moccasin bites Gram Hiddle's leg could be seen as symbolic in any way? We know that might sound like a stretch, but hear us out.
Nature is very, very important to Sal and to her family. She respects it more than anything else. She longs to be back in Bybanks with her trees, her farm animals, her fields, and her sky. Nature seems to have healing, magical powers. However, at this particular moment, it is incredibly harmful, even potentially lethal. Though Gram does not die from this snakebite, her health declines rapidly after it.
So what are we to make of all this? Well, the snakebite just might show us that nature is very unpredictable and very, very uncontrollable. Like life, nature causes hurt and pain just as much as it brings us joy.