Hey Rob,
Well according to your previous calculations it's only day 25 since mating. She just may not be ready yet. My female looked like she was going to explode before she started digging and she only laid 26 eggs. I can't even imagine how some of these chams look before they lay 50-70 eggs!!
I don't think you mentioned if her enclosure was mostly covered or not. They need an added sense of security when laying eggs. They want to be secretive and think that nobody knows where they're laying their eggs. I don't think I'd be too concerned unless it gets to day 30-35 and she still hasn't started digging.
Is she still eating occasionally? She likely won't eat much but should have something to keep her strength up. I was putting a bit of the calcium powder in the water I was spraying to help keep the eggs calcified.
They like to keep us waiting don't they!!
Dyesub Dave.