My oldest has waist length fine hair too. I have found that the salon brands make all the difference on her hair. I try to buy it in the fall (back to school time)when they sell it in liters. Normally you can buy them 2 for $25. Then I buy the $1 pump and it lasts a long time, plus as a bonus my younger two cannot waste.
Condition well, and make sure it's all rinsed. Buy her a nice high thread count pillowcase, or a satin one (Hannah's is pink satin and she thinks it's "princessey") I buy the conditioning spray for mornings, again the salon brands are better ingredients and go further, I do use the suave apple scent on my two younger ones though.
I bout dd the American girl book about the care and keeping of you. Also they have a book about hair I got for her too.