Try a lay box. I use a large rubbermaid bin filled with about 1/3 with good top soil from a local supply store or lowes menards ect. Use some warm water and make the dirt to the consistancy of a snow ball (meaning you can squeez the dirt and it will clump up, dont get it runny). If you can cut a hole in the top of the rubbermaid lid and staple some screen on top of the whole for the light, or if you can not just clamp the light on the side and pay close attention she does not escape. If she has slugs she will dig and lay them and she will feel alot better
She will not be attached to the eggs in any way so after she has done her business and burys them you can take her out and put her back in the cage and throw away the eggs!! Do not give her a bath for 2 to 3 days because its said the water can get in the vent and cause an infection. I dont know if this is a fact because i have never risked it lol!!
I hope this solves the problem, Good luck!! If you have any questions do not be afraid to ask