Corn is fine to give in small amounts it can put on pounds so you don't want to feed a lot. I know quite a few members who feed their flocks chick starter /grower as their sole ration I don't see any problem with it but you want to make sure she gets enough niacin too which chick feed doesn't have . Maybe put some Nutritional yeast sprinkled over her feed a couple times a week for the B vitamins it contains. and once she begins laying she'll need oyster shell for the calcium to give her eggs a good hard shell. Nutritional yeast dose is 1 Tablespoon to each cup of feed she eats. Mine get it a couple times a week .