Certainly there are some diseases that are so fast that a chicken can seem ok in the morning and be dead by nightfall. But the vast majority of diseases have symptoms other than (or anyhow, prior TO) death. If you never saw anything wrong with her, and have been reasonably observant about it, I would not be quite so quick to conclude it was a disease.
Chickens sometimes do die suddenly without warning, particularly pullets relatively new to laying. Stroke, heart attack, I dunno what technically but that sort of "physiological accident".
If it were me, I would try to examine the carcass carefully for any hints of something wrong, insofar as you can tell 'something wrong' from the normal results of death (blood pooling darkly in lower and downward-facing regions) and from postmortem being-pecked-at. In particular, check her vent to see if there is any sign of diarrhea, blood, or egg debris. (Diarrhea would suggest, although not prove, possibly-contagious infection; blood would suggest possible prolapse or laying difficulties or fatal pecking; egg debris would suggest laying difficulties)
Then I would also carefully examine all the other chickens, paying particular attention to their vent area but also seeing that the comb and nostrils and eyes looked normal and checking closely for mites/lice.
Unless you find some particularly-suggestive signs or problems, I suspect you can probably chalk it up to one-off bad luck.
Condolences and best wishes,
Pat