could be she lost an ovary..most likely from infection..
might be a good idea to give antibiotic..Amoxicillin is an option::
http://www.firststatevetsupply.com/store/index.php?cPath=21_30
you might be able to get small amount cheaper from a vet or other source...there are other options a vet might suggest..
most likely she won't be laying any more eggs..
(unless this is the "dead" ovary..hens are born with 2 ovaries, but one "dies" leaving only the working one)
best to give this girl some extra protein..(boiled eggs, etc..)
some Poly-vi-sol liquid baby vitamins..no iron..3 drops on beak once a day for a week..then taper off for another week.
keep in warm safe place..and give TLC..
you can make up this mix..
this is for 1 day..divide into 3 feeds for the day..give for 5 days..
along with regular feed..
1 cooked egg yolk
small drizzle of honey and/or baby applesauce or unsweetened applesauce
2 tablespoons plain yogurt
2-4 tablespoons baby oatmeal cereal or cooked regular oatmeal
make mix puffy..not soupy or gummy..add layer feed if necessary.
has the hen been wormed?
describe the droppings..color and consistency.
if you opt to take her to a vet..or get meds from a vet..(preferably an avian vet or vet college)
take the sample "egg" for lab tests, just in case it's something else..