Hi, missionarywife.
I can offer what I have read or heard until someone with more direct experience can step in.
Different ducks handle things slightly differently, but generally the concerns are safety and that she have water and food near enough that she feels comfortable getting up and feeding and drinking for herself regularly enough to keep up her strength and health. She needs to be safe from predators. If she has chosen a spot outside the usual safe place, some people build a little pen around her nesting spot to protect her.
She is not likely to be patient with anyone or anything that disturbs her.
She may not groom herself as usual, and could start looking a bit raggedy.
It takes 28 days for duck eggs to hatch.
Some ducks aren't great mothers, even though they may set some. As time draws closer for hatch, somehow keeping an eye and ear out for ducklings may help prevent losing them.
Muscovies lay many eggs before beginning to set. Other breeds lay fewer. How many eggs does she have? You may not be able to safely get close enough to know.