If its egg related then in an ex batt it may be you are fighting a loosing battle with this girl.
You say something that looked like a soft shelled egg? Can you break it open to confirm it. A soft shelled egg isn't unusual and certainly on its own nothing to worry about (increase oyster shell intake). Many hens lay them from time to time. But it could be she has something else going on in that department that is problematic. You also described about her losing some of her insides. If you mean there is some blood and stuff in her droppings chooks can do this also and if its what I think it is, again its not a disaster.
But having said that, the fact she is clearly not right, her eggs are soft and she is shedding her stomach lining, it does make me think there is something going on that she may not recover from.
It may also be worth you taking a sample of her droppings for analysis and your hen to the vet. Is your vet experienced in poultry? Tylan and Baytril are the two things most often used to treat chicken related problems. Anything else and I'd be wary tbh.
I hope your girl picks up but knowing her history (ex batt) and how this can simply wear their bodies out, prepare yourself she might not pull through. I've had hens like this and after a few days of this kind of thing I've culled them as it seemed the kindest thing to do. Others have perked up but then within a few weeks died coming down with the same sort of thing again only this time dropping off far more quickky.