late developer

Last May I bought 2 11mth Speckled Sussex, 1 of which sadly developed Marek's disease and had to be put to sleep. The other, Splish, has been freeloading from day 1 - until last week when she laid her first egg!
She then laid another, had a day's rest, and then laid again, but this time she ate it, as with the next one, so I kept an eye on proceedings yesterday and managed to rescue the egg before she got to it. From the racket she made announcing it's arrival I assumed it was huge & had taken considerable effort. How wrong I was...
She has only eaten her own so I wonder if, after all this time, it's come as a bit of a shock to finally be laying and she's trying to hide the evidence (not very convincingly when left with yolk on her face)
The photo shows a normal 65g egg on the left, Splish's first egg (50g, large yolk - ideal for mayo!) in the middle and the "huge" 14g egg from yesterday.

Yep, she always leaves the evidence and it seems tough enough, no weaker than the ones she left - although the first 2 were laid in the nest box and the eaten ones were found on the ground under the ark, also where the diddy one was laid.