I really would consider the vitamins, since it will not harm her. Riboflavin deficiency is quite common, even with chickens getting a balanced feed. You can Google riboflavin deficiency in chickens and will find quite a few articles. The earlier it is treated, the better the chances of improvement. Your friend may be convinced it is Mareks, but I would at least try some BComplex, riboflavin, or poultry vitamins. Plain yogurt, chopped mushrooms, beef liver, and other foods are rich in riboflavin. Many people see results in a week or two.
