I had one lovely little hen that just was more prone to having soft-shelled eggs and would occasionally get egg-bound. Despite have the same diet and access to oyster shell as the others, as well as being the same breed. We tried giving her calcium but that didn't seem to affect the rate of it happening to her. Maybe an issue with her ability to absorb it?
I think I removed a flat, empty, squishy egg shell from her more than 10 times over 3 years. She would otherwise lay 5-7 normal eggs every week. When she wasn't feeling well the only thing she owuld eat ewas wet cat food. She was the lowest in the pecking order but for wet cat food she would kamikaze launch herself over the other, bigger, chickens.

Thanks for letting me relive my "Chicken Little" adventures a little bit.
I am sorry your little hen died. I hope you have many more chicken adventures in your future! The joy is worth the pain!