Sunlight, Vitamin D, the right fats - these certainly all play a part - the concern I would have is this: you spoke of crystals forming - in my experience, this usually means some kind of parasite. Normally, when people get the kind of skin condition you are describing, it usually appears on the legs, but when the body is trying to push something out through the skin, it can erupt any where. If I were suffering with this condition, I would go on a parasite cleanse along with cleansing the liver and bowel. If she is eating alot of Salmon, she is getting some good fats, but may not be getting the full spectrum, so I would also look to my diet to make sure I had my bases covered.