Firstly, welcome to the forums! This is a great place to learn about chameleons and meet other keepers.
Exo Terras are fine for chameleons. Aquariums are not fine because they don't allow for proper ventilation, but yours isn't an aquarium.
Your tank looks pretty nice overall, but I also recommend taking the soil out, especially because your cham is so young. She can easily become impacted from accidently ingesting even a little of that dirt at her age. Most of us just use newspaper or paper towels on the bottom of our cham cages (and change them frequently).
You shouldn't worry about humidity because as long as you mist 3-4 times a day, the glass will hold in the humidity just fine.
I would recommend some more foliage for your cham as well. Live plants (such as pothos) are wonderful. Just plant them in a pot, and cover the soil with river rocks to eliminate the impaction risk. That's what I do in my baby cages.
If you post pictures of your chameleon laying on the dirt it might give us a better idea of what could be going on. Sounds like it was just way too hot in there though. Remember, chameleons can't sweat or pant to regulate their body temperature, so you have to be extra careful not to let them get too hot. Especially in a glass tank that small, you'll be much better off airing on the side of caution and keeping her basking spot temp fairly low. It's best for them to have a temperature gradient with the cage floor going down into the low 70s, but it's hard to create that type of gradient in a small glass enclosure because they hold in so much heat.