Both my females dug test holes for 3 days before being 'happy' enough with the tub to get on and dig for real on the fourth day. The whole process can take all day, as they begin digging when it gets light and have to dig down and make a tunnel/hole, then they turn around and go bum down in the hole where they lay the eggs. After depositing the eggs they then cover them up and fill in the hol again. They really push the soil back down very hard, so much so, that is is quite difficult to dig them up after!
Don't let her see you watching - Most people cover the front of the viv whilst the female is laying. They are less distracted as if they abandon the site often enough the urge to lay will pass and she may become eggbound.