Others have answered the "smell of" part.
When you say "a hint of X", you mean just a small amount of X, or that X is there but difficult to detect. Like if you said, "This cake contains a hint of chocolate", that means that it is NOT a chocolate cake, but there is a small amount of the taste of chocolate to it. Or I heard a politician just recently say that "there is not a hint of corruption" in his actions. He means, there is not the smallest, tiniest amount of corruption.
Note that this sentence is not literal. She might smell like daisies, but she probably does not literally smell like the sun. I don't think river water really has a distinctive smell, either. It's all a poetic way to say that she reminds one of pleasant things from nature.