I don't use leave-in conditioners like a regular conditioner. Use that as an extra defense. Use regular moisturizing conditioner and only rinse partially. Use it liberally, and make sure that you can still feel it a little after you rinse. THAT will be your leave-in conditioner. Then, you can apply actual "leave-in" conditioner, as well. Or jus tapply the leave-in before swimming. Pull her hair up into a ball on top of her head or braid it for swimming. Don't leave it "free" in the pool on a daily basis.
My hair is very sensitive to the elements. In summer, I keep it covered in the sun, or it will literally fry. When I know that I'll need to expose it, I apply conditioner and coconut oil. I might as well let that localized sauna-fire work FOR me. (When I'll have it covered while still in the sun, I might include almond or castor oil for extra conditioning. I alternate to shake it up a bit.)
With your daughter, maybe a good daily rinse would work better for her hair, and then shampooing twice a week.