All my Muscovy's are housed together. But I can start separating him now. He mates all my girls as soon as they leave the nest for food and water breaks. And no she won't be taking care of the ducklings once hatched. I will be taking them to the Jasper County Fairgrounds Animal Swap June 18th. Her eggs are due to hatch within a week of June 18th.
I'm like Faraday, I only know chickens and turkeys, not ducks. But if she is sitting on eggs, I would venture that she is not mating with the male anymore. With turkeys, I have read that once they lay their fertile clutch and go broody and sit, any leftover sperm gets destroyed. (Not sure how true that is.) So if she's been on eggs a while, and you have a way to isolate her, then I'd say that you could probably go ahead and mate her to the blue male right away, when she is done being broody. Is she going to be hatching these eggs and raising babies? Maybe you can get her over to your friend's before she starts mating again.