Hi, sorry to hear about your chicken. And sorry you didn’t get a lot of help before. Can you post some pics of her? Sometimes we can see some things that could help figure out what is wrong.
How old is this hen and is she laying currently? What is her diet? When was her last egg?
Let’s start with some basic checks to rule out possibilities.
How is her crop this morning? It should be completely flat in the morning and full at night when she goes to bed. The crop will empty overnight when everything is functioning properly. If her crop is full still when she wakes up, she may have an impaction.
Mites seem to be very persistent right now with the chilly weather, can you give her a really good once over for mites? Check primarily near her vent in all her butt fluff. A dirty bum and tail down can be a sign of mites or lice and they really can take a toll on chickens when contracted. One of mine contracted mites and struggled a bit more to stay warm in the cold.
Also check her abdomen, right below her vent, sort of between her legs. Is it bulgy at all?
Does she get bullied or kept from food?
Check all her openings - eyes, nose, ears, mouth. Any discharge, lesions or bubbles?