T.M.
My husband has similar hair although he cuts his short :-). I've tried Aubrey Organics and I've read reviews about it and it's wonderful for the hair that you're describing. You need the tiniest amount and although it's expensive it can go a long way if you only use it sparingly. It sounds like she really doesn't need the harsh chemicals on her hair. I'd go lightly and wash her hair maybe 2-3 times a week at the most.
You could include some fish oil, they have lemon flavor now, to help with it but I'm not certain it would help if it's just the kind of hair she has. Wild Oats carries a brand called Carlsons which is wonderful.
Good Luck.