I have 1 muscovy drake and 3 hens. There was one who started laying in fall. She was/is ostericised but, she does well. There was never any blood, but feathers pulled. I don't see her eat and drink as much, but she is the most friendly of the hens and picks on my pant leg for a treat.

I spoil her a bit more, so maybe the others take that into consideration?
I've thought of adding another hen to even it out, but have been told that it may or may not help. I guess sometimes it works like this. I'm almost wondering if your hens are meaner to her than your drake? I would observe to see who the real aggressor is - unless you already have. My drake tends to like this hen a bit more than the others, so I think that also plays into the aggression that I see from the other 2 hens towards her.
Good luck!