[LunaTheHamster1]

Like you said that is exactly one of the ways they can escape.
What type of cage is she in. is the wheel attached to bars or free standing?
Does the cage have a lid?
I would suggest she would probably just chew through the cardboard, but you could give it a go.
I would just make sure there is bedding around the back of the wheel so if/when she falls she has a soft landing.
If the wheel is not attached to the cage, the only other thing I can think of is to move the wheel away from the side, if that is how you have it placed. Or to actually attach it to the side of the cage if that is possible.
Others on here may have other ideas.