If you can't fit the container you made up in her cage, you can use an opaque container a minimum of 12" x 8" deep X 9" in the cage filled with moistened washed play sand. This gives her a place to dig when she's ready so you don't miss the often subtle signs (and she may even lay her eggs in this smaller container) and you can move her to the bigger container once she starts to dig. Make sure that when she's digging you don't let her see you watching her...it might make her abandon the hole.