K.M.
There are many great deep conditioners on the market, Wen (mail order) Bigelow products (very good), but all these are topical. Have you tried a humidifier (if the air in your home is dry) as well as treating your daughter's condition from the inside out? Such as adding more fluids particularly oils to her diet will help. Obviously, her age will dictate what you feed her. Check with your physician. Perhaps adding a teaspoon of olive, flax or another healthy oil to her diet daily will help. I know it helped my daughter and myself in treating our dry skin and hair. Again, check with your physician and use common sense. Add it slowly and gradually to her diet as her bowel movements will also be affected and will indicate an adequate dose for her. Happily, if she has any constipation issues, this will help that as well, but again, common sense, you don't want to create another problem while fixing one. Honestly, adding a little oil (mixed in with her food) to her diet should really make a difference in her hair and her overall health. Actually, the one my daughter and I and my whole family take now (I take capsules) is castor oil. Sounds awful and old fashioned, but it really, really helps many things, not just dryness. It is a great, I mean great source of vitamin D which many of us lack due to limited sun exposure and lots of healthy sun screen. Try it yourself. All the Best, K.