I moved her and her mate into a separate hutch from the chickens they were with. If she sits, we’ll see what happens I can always put a heat lamp in there and really insulate it well. It’s only three eggs so it shouldn’t be a big deal. I won’t let her hatch more than five
If you can use heat and keep them secure it may work. I normally heat nothing but one year a Muscovy female had a clutch in Feb, i did have to offer her some extra heat but they all lived and thrived! I do know calls are more delicate but.. that is usually only at the very start after that IMO/IME they are the most hardy of ducks mine are insane for their overall hardiness.