Then she has a very natural day and night cycle.
She's a young layer and this isn't uncommon with them. The cause is a brief interruption of hormones, causing the yolks not to be released. Instead, a tiny piece of tissue from her reproductive tract gets egg white and a shell and you have a...
For some reason, her ovulation has been disrupted. This is not uncommon in much older hens or when a hen is approaching molt, but to have this in spring in a fresh layer, it doesn't bode well.
If you have an avian vet in your area, this would be worth running by them.
Is she under supplemental...