Put her on chick start crumble feed for a week or so while she gains her appetite and strength. Make a warm mash of it which may appeal to her. She probably isn't laying right now as she has been ill, so she doesn't need the calcium in the layer feed, which she may be sensing.
Most hens love the flavor and extra protein in the chick start.
You can also supplement with yogurt or sour milk in the mash. That is high in protein and probiotics, which is important after the round of antibiotics. This will aid in her digestion, which is likely sluggish right now due to her gut being off from being sick.
Also place Apple Cider Vinegar in the water (about 1TB per gallon). That aids in the digestion as well as it feeds the good probiotics in the gut.
Black Oil Sunflower Seeds (BOSS) is high in fat and high in protein, and another good supplement.
In time she'll likely be back on the layer pellet. If not, she could stay on an All Flock crumble with oyster shell or calcite grit free feed for calcium needs. All your layers could be on that regiment.
Some hens don't prefer pellet ever. Others have trouble digesting it after coming back from illness and like having something more easy to eat and digest in crumble, with the higher protein. My hens prefer higher protein feed during the winter months when cold stress is an issue.
Edited by Lady of McCamley - 2/2/16 at 9:21pm