I would use whatever you have right now. She may not want to eat right now. Ducks often stop eating while they are egg bound. So it you will likely need to administer whatever use orally. The calcium tablets would probably be the best solution. You can try softening it up in some hot water. Or...
It sounds a lot like an egg bound duck. They usually pump their tail too. I would put her back in a bath and leave her their for 30 plus minutes, hour or longer. The water will help facilitate laying. For this, the best thing to give her is calcium gluconate. I get it at TSC, and it is labeled...