I have extremely fine hair, and all through my youth it was so dry it made a fine nimbus around my head of fly away hairs and frizz. I tried all sorts of fancy shampoos and conditioners and hair oils but it was expensive and I couldn't keep it up.

What worked for me was to stop buying and using shampoo altogether, and wash my hair less often. Instead, I use a paste made of rye flour (has to be rye, not wheat) in the shower on my scalp only when it's getting noticeably greasy. Then, I use a normal daily conditioner and rinse it out after a couple of minutes. The rye flour is messy and a pain to rinse out but I am so much happier with my hair now. It's soft and shiny and falls the way it should, and has much more body to hold waves and styling.

I agree with other posters that protecting her hair from the pool chemicals is probably the biggest thing that will help. I also think an oil treatment like coconut or olive oil would help.

Here's my suggestion from one fine haired girly to another:

Have a spa day where you comb oil into her hair (coconut, olive, avocado, etc), leave it in for at least a half hour, and then wash it out using a rye flour paste. I know it sounds kooky, but it really does work. It gently absorbs excess oil without stripping it from the hair, and its ph balanced. After rinsing the flour paste from her hair it should be soft and hydrated but not greasy. If you don't like the results or it doesn't work then nothing is lost, just have her wash her hair again and make bread with it or whatever, but I'm serious it saved my hair.