I would use paper towels for the quarantine period. Much much easier to clean and see things like mites if they should show up later down the road. You can use tinfoil or wax paper to cover the screen lid (tape the edges down) to help hold in humidity and you might have to mist every few days during this period to help with that too.

Once you move her out of quarantine, use whatever you like best. If the eco-earth works for you, use that. I personally found it to be too "dirty" for my ball and I use cypress mulch instead. That holds humidity just as well as the eco-earth and better than the aspen, but its cleaner and easier for me to keep clean. Just a thought and it's mostly just a matter of preference. But I would definitely use the paper towels for the quarantine.