what all do you feed?
have you treated her for mites?
has she been wormed?
describe the droppings..color and consistency
do you give oyster shell or any calcium supplement?
sometimes the loss of a companion, especially when there are only 2..causes stress..and they will stop laying..
chickens are flock animals and need to be with other chickens.
they will also stop laying if they have worms..and a mite or lice infestation..which depletes them of nutrients.
if she is in molt..she may need a protein boost..such as cooked eggs, a little canned cat food, or a little dry kitten feed..
vitamins can help also..
if you don't have access to poultry vitamins, until you can get some..you can use Poly-vi-sol liquid baby vitamins (Enfamil brand, no iron)..2-3 drops in beak once a day for a week, then taper off...