I had to laugh, breaking a broody Muscovy is not something that has gone over well here.
When my grumpy hormonal Muscovy girls start picking on each other the one that's doing the pecking gets to spend however many nights it takes by herself, usually only 1-2 nights. But when one is broody and sitting on an empty nest or eggs I take the eggs and usually just let her work it out as long as she is nice about it. I've tried many ways to break since 2004 [thats when I started with this breed] and not many work. I've torn up the nest, locked them out, and it doesn't seem to matter.
You might just let them be together but with fencing in between until your Muscovy gets over it. Usually mine only seem to get really hateful is at night when they get locked up in their house. The rest of the time they have plenty of room to stay away from the crazy one.