Here's how it should go...
Provide her with an opaque bin at least 12" X 12" X 10" deep filled with washed playsand that is just moist enough to hold a tunnel. Make sure she can get to it.
She may dig several test holes but should set le on one and dig it until she's happy with it. Do not let her see you watching her once she starts digging. She will then turn around butt down in the hole and lay her eggs. It's will likely be in the evening. She may stay in the hole all night. When she's done she should fill the hole in and tamp it down and return to the branches thin and hungry and thirsty.
If it doesn't go like this and she sits low in the cage, sleeps during the day and is lethargic...it means she may be eggbound or heading towards it and needs a vet ASAP.
Hope this helps.