Eco earth, Reptichip, and other coconut-based substrates hold humidity well, so the same stuff You use for your gecko should work (all you have to watch out for is that they don't accidently swallow a whole bunch, but you have to do that for any substrate). You can also give her a bigger water bowl, and try wrapping the top in tin foil:
https://ball-pythons.net/forums/show...tment-Tutorial
How are you measuring humidity? What's it at right now?
I could be very wrong, but if I were you, I'd try and stop the heat from getting over 90f. In my opinion, anything over that's too hot, but hey, that's just me.