I think the open space is probably the problem.
To begin with I would completely fill the base with substrate right up to the top of the plastic, that should help.
She really needs a bigger better house than the igloo, plastic isn't too good as it gets quite humid in there & the igloos aren't completely dark.
Would your wheel fit on the shelf or is it too tall?
I was just thinking if you could put the wheel on the shelf you could put a nice big shoebox size cardboard box house there, no base & a door cut out maybe with a bendy bridge in front of the door to make it really dark inside.
If not then maybe you could get something similar under the shelf?
If you leave the wheel where it is you will need to buy or make a shelf to stand it on so it's above the level of the substrate, you can easily make one with a piece of safe wood & some dowels glued on for legs.
Then you need to put more into the open space that's left, things like cork tunnels or tubes are good or even more bendy bridges to make little hideouts & something to climb on as well.
Hyacinth or seagrass tunnels are good too & available from most pet shops or online, just check they're big enough as they come in different sizes.
If you use cork it's best to put it in a bag & freeze it for a week before use just in case of bugs!
Have a look through this thread for ideas of things to use & how best to make use of the space you have.
Let's see your cages - New thread - July 2017