Maybe the creature uses salt to regulate her electrolytes and body fluids, and just needs a lot more of it than we do. She's consuming other stuff off camera, such as water, carbohydrates, proteins, and fats, and then she needs copious amounts of salt to drive the plot.And eventually, I realized that the whole premise of a species that metabolized sodium chloride was utterly preposterous... given that it's almost impossible to tie up sodium+ ions or chloride- ions into something insoluble, that would keep them from finding each other and re-forming as common salt...