Sorry that you lost her.Your state vet could do a necropsy to find out what killed her if you wish. I usually do a home necropsy on my hens to learn what they had wrong. If you do the latter, post pictures here for any advice. There is a good video of a chicken necropsy with organs identified if...
Some people don’t worm, but with one that is having unknown problems, that is what I would do. Then, I would just give her an all over exam for the things I posted above. Weights may be gotten with a kitchen scale or weighting a chicken on a flat surface while holding them, and then subtracting...
Very often a hen that age may suffer from a reproductive disorder or a crop problem. Has she been laying recently? Has she lost weight through her breast muscle or is the breast bone prominent? What color are her poops? Pictures welcome. Is her lower belly under her vent enlarged, spongy or...