Rain Dance + Surf is great for Charlotte, even in the superheated field. And about Electric types, you can pick up a Rotom when you're able to return to Reborn City by doing this event:
(It also shows you how to get Solosis, which is useful for Trick Room + Psychic)
Then all you gotta do is pick up a Data Chip, restart a computer in Ametrine Town (you'll get there after Charlotte's gym), and them you can choose the Rotom Form you'll want to run. Rotom doesn't have many moves, but it has Pain Split and Double Team, both of which are very annoying.