What are the humidity levels in
your place? If
your hands feel very dry, then
your cat might be experiencing this as well.
Check her for parasites, fleas, mites etc. Is she indoors or outdoors?
Most over the counter products don't work but perhaps there is something out there that can help her, depending on what the cause for her dandruff is. I personally don't know of any good products to get rid of dandruff. Hopefully, somebody here can help you out on that.