Do you have a video of the duck?
If she is outside, could you move her inside into a warm, humidified area?
If the bird isn't drinking well, fluids must be delivered via gavaging, or subcutaneous injections, as birds with egg-shell issues currently dehydrated show a grim prognosis. If the bird is drinking well, you may just consider adding an electrolyte to help her stay hydrated.
Calcium is often indicated with egg-binding issues to help promote muscle contractions; for that, you could use calcium gluconate 23%, given at 0.2ml per pound, orally, or opt for other calcium supplements such as citrate, or calcium carbonate (found in tums). Soaking the rear side of her body in warm water may allow expansion of the surrounding tissue in the oviduct allowing easier passage of the egg.
Any egg contents visible externally may be able to be pulled gently with a pair of tweezers, or forceps.
Antibiotics will sometimes be recommended if the egg contents are stuck in the oviduct for an extended period of time.