Tresemme products always made my hair look really bad - you might try switching. Also you might look into using shampoo less often if her hair is dry, although you will have to be sure there isn't hair product build up.

Lastly it may also be a health/nutritional/food allergy issue - do you think it is possible she is not getting all the nutrients she needs or is allergic to some foods? For instance if I eat cow dairy products regularly, my hair grows out very frizzy and also falls out some.