Mouse hoppers are pretty small.. you may want to bump it up to a small mouse.. or feed two if you think she's still hungry (cruising around the cage after she's been feed like she's looking for food)

I feed all of my snakes in their enclosures.. ball pythons are ambush predators.. it's more normal for them to lie in wait for something tasty to come along. I guess there's nothing wrong with putting the snake into an enclosure that already has the mouse in it.. if she eats, but it's simpler just to feed her in her cage.