Once they go full broody [have laid all the eggs they want to brood and in their minds they seem to know] They do stop laying and go full time broody.
Has she lost feathers on top of her head? down to skin ? that is one way of knowing she is getting singled out if none of the other girls look...
The eating and drinking more sure sounds good. So she may not be having egg issues all we can do it eliminate and start with what can usually happen if one of our females is acting off. So check in tomorrow and if she is acting completely normal eating good mingling with the flock and still no...
One member had to give it I believe at least 4-5 times before her duck laid. Even if she isn’t egg bound it won’t hurt her to have it 3-4 X just keep it in the frig so it stays fresh in case you need it again.
Here is info on Cal glu
https://www.backyardchickens.com/threads/calcium-gluconate-for-egg-bound-ducks-preliminary.959537/#post-14940303
here is the best way to give it by mouth without aspirating them...
Do you have any calcium gluconate Just in case she may have an egg stuck? 1 ml by mouth we have info on how to give meds by mouth. Do you put out oyster shell?