I think you should start her off with protein treatments. Protein helps shore up hair's internal structure to give the waves shape and the hair body. Should also help with the damage. The Ion effective care packets may be a good place to start. Since her hair doesn't need much moisture, she may not even had to use a conditioner after the ion PT. When her hair has more protein, it may react better to conditioner.
Other then that, I'm not the best person to ask. My hair can take lots of moisture and fairly heavy stylers. Here are some guesses.
Giovanni Direct leave in. It has some protein in it too. I don't think it is too heavy.
Spiral solutions firm hold gel. It has pretty good hold, but doesn't have much of a styler feel.
Switching to a low poo would be good too.
a microfiber towel to dry hair. Tell her to squeeze the water out, and not rub.
(blog to help new wavies)
2a (nc.com) 2bFi (Fia), very fine, thin, low/normal elasticity, porous, CG, doesn't get weighed down
Cowash: Tresemme naturals
Rinse out/leave in: Renpure Organics (red)
Curl enhancer: FSG
Gel: BRHG, Salon care aloe, Ecostyler Krystal (normal dews)
PT: ION effective care, IAgirl's gelatin PT
Low Poo: renpure (red), Ion swimmers