Since you didn't tell me if it was her first breeding, I will assume it was....this is my opinion of what I have seen happen. I have no documentation to back it up....just my experiences.
What I think happens is this....it seems that depending on where a female was in the cycle when mated she may have had (infertile) eggs that were too far formed to be fertilized. These eggs seem to be dumped fairly quickly after the mating (thus the 21 day laying). The next clutch should be fertile eggs that are produced from the mating....and for some reason, they seem to be laid sooner than the normal 30ish days. The only thing that is bothering me about yours is that you said she dug at the 35 day mark from the mating and then didn't dig for the next few days.
Have you been letting her see you watching her when she is digging?
How is she? Is she acting normally...eating, drinking, etc. or is she lethargic and inactive and has her eyes closed?
If you suspect that she is becoming eggbound, then I can only recommend that you get her to a vet ASAP.