She quite possibly has a genetic weakness that allowed the wall of her tract to rupture and this allowed the intestines to spill out of her vent. If it were a predator, she would be dead. Even with a prolapse and picking, it's doubtful she'd expel that amount of intestines without a very large amount of blood. The other hens would've killed her.
I've experienced this as a genetic weakness in a line of ewes passed down from a ram in my flock when I first started. Every ewe met the same demise, we usually found them dead with the intestines trailing out behind them. If found alive, the ewe was quickly dispatched. Consultation with our vet confirmed there was nothing that could be done without enormous expense and the that didn't guarantee any results.
It's very possible she was in the nest box to lay an egg. The straining likely caused the tear and subsequent result.
I understand what you're saying and although I agree she most likely would be dead if this were from a predator I know from many personal experiences spring of 2017 that this isn't always the case. Unfortunately we had a very bad beginning to 2017 that involved losing most of our juveniles to rats that were 12-18 inches long not including the tails, some even longer. These rats were predatory and would attack the unsuspecting birds while they slept(although at this point they were large enough and the juveniles small enough yet to overpower the birds). They would then eat into the vent and would eat out the intestines of the birds. We found many dead of course but about 1/3 we found alive and walking. With no digestive tract. These birds were of course put out of their misery immediately. It is possible that some of the aforementioned attacks were from the mink although we had no clues it was around at that time. However we did catch rats in the coop so we know the were a large part of the problem if not the whole problem.
We also later discovered that we had a mink that was also possibly attacking and killing our birds.
Thirdly yes we do know once the body cavities opened and the innards spilled out the blood did attract the other juveniles. However they never opened their hatch mates themselves or it would have continued after the rats were dealt with.
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