Sand is fine for chicks but it will pass right through a hen. As she grows, a chicken selects larger and larger pieces of grit so that the pieces fill her gizzard and stay there working to grind her food until they are worn or outgrown. At that point, they pass through. Think of a larger straw and a smaller straw with a pouch in between. A grasshopper and grit go in the bigger straw, reach the pouch where neither can pass through, and are churned around by muscular action. The ground up grasshopper now fits in the small straw but the grit remains for the next meal and the next and the next until it loses enough size to travel down the small straw with the food. The harder the grit, the longer it stays in the gizzard. Sand would pass through the small straw and might help a bit with the grasshopper but it would be much more effective for her to have appropriately sized grit.