Okay, this is what I would do: I would keep her in her regular cage with a small bucket or bin filled with dirt. When you notice that she goes off her food and is starting to spend time at the bottom of her cage and/or inspecting the bin move her to the larger lay bucket.
I would also ignore her! Beyond the daily feedings/misting sessions and maybe some spot cleaning I would not watch her, handle her and generally not torment her.
Good luck! I know you concerned and that's great for a new owner! Just remember, these animals have been reproducing for thousands and thousands of years and therefore she knows what to do. Just give her what she needs and everything will be good. Also remember that chameleons are a "look, but don't touch" kind of pet, so just let her be. You are just stressing her out more by being stressed out!
Cheers!
T