You can try tea tree oil, there are a lot of products out there that contain tea tree oil, or simply try this recipe .... One cup of real mayonnaise with one ripe mashed banana mix well and apply to hair dry or wet let sit for about 5min and wash hair out with a shampoo that is a two in one like Aussie clean from root to tip its great ! Or you can get hair cholesterol from the drug store it will help also , sometimes if you wear your hair in a ponytail to much or a hat your scalp can't breath thus causing flakes .
Polytar plus is a good product to cure the dry scalp. You should also give massage of olive and coconut oil to your girl. It will do wonders for you. Please also visit the link below to see the answers of other people around.
You should try a sensitive dandruff shampoo