I would first look at how much salt is in her regular diet. Most people already have more then what is recommended. I think you’ll find that most people don’t need extra salt as a replacement for what is lost via sweating. The best thing is to make sure they are drink enough water.
We always pack frozen grapes in the cooler and use them as the "ice" to keep her drinks cold. Just like others we do alot of fruit due to the hydration factor of it and with it being frozen to start it will help her cool off between the innings.
Pack what they'll eat that is relatively healthy, and just drink water and stay in the shade in between games. Our regular pack includes sliced celery, peppers, lots of fruit, pickles and peanut butter crackers.
Thanks for everyone's input. She turned out to be one of those players who doesn't really eat much during the day because she's too keyed up and it made her feel to slow in the next game. I had a cooler with tons of water and then a sports drink after. We come from Tucson so drinking water is like a religion to us, staying hydrated in San Diego heat even for a catcher wasn't hard.
Really just focus on what sounds good to her. Mine is a pitcher and when they are hot and tired and running on adrenaline it's all about what sounds good and hydrating. She will usually want the fruit (grapes, cherries, watermelon, berries) maybe half a sandwich after each game, a pickle (she now has our whole team really into pickles we've been going through a couple jars in a day), olives, fishy crackers or kettle chips, sometimes a string cheese . . . She hates sports drinks and power bars etc on these days just wants real food with no fake weird after tastes she says