If you're dealing with dandruff and thinning hair, I've got a couple of great budget-friendly options for you: Nizoral, which contains ketoconazole to tackle dandruff and might also help with thinning, and OGX Biotin & Collagen, which really boosts volume and thickness. If your scalp is on the sensitive side, Dove DermaCare is a nice gentle choice.
Have you or your daughter given any of these a shot? What's her hair type?