Branching off what Homegrownscales said, you can use your rock hides, but many snakes tend to stress out more if their hides aren't tight. Balls like being able to touch all sides of a hide. Perhaps use something smaller temporarily until your little girl grows up a bit. Or you can stuff it w/ crumpled paper towel/newspaper to fill up the extra space.

For all my hatchlings, I use dollar store small plastic bowls and cut a hole in for a door. They're the perfect size for my babies and really cheap (3/$1).