Tell your cousin never to use that dye again; it has got very powerful chemicals in that.
For her hair dryness ask her to try some moisturizing cream on her hair. This time check well if her sensitive hair can stand the cream.

Add moisturizer to the hair-that what you can do. But you need to be selective where moisturizers are concerned. There is another solution which is to massage your scalp with egg yolk. Egg yolk is very nutritious and can thus provide some nourishment for the hair. In addition egg yolk will make the shiny.

You mean that her hair is graying. For this I can help you.
Do you know curry leaves? They are considered to be beneficial for preventing premature graying of hair. The leaves are able to provide vitality and strength to the hair. Consume them as much you can. The leaves are used mostly used as spices. So, don’t forget to add them in your dishes.