Sounds like pneumonia from housing her. She needs an antibiotic straight away - I use Terramycin LA for lung things. You also need to keep her moving. Stand her up at least every two hours, using bales along her sides to hold her up if necessary, but not under her tummy as that will put too much of a strain on her heart, lungs and digestive system. She will need to stand to burp and pass urine and droppings, plus of course lying in one position cuts off the blood supply to the legs.
When did she last drink? You can use a large syringe (minus needle) to get fluids into her.
With sheep, it's always best to treat immediately you notice something is not quite right as they can die very quickly