What's wrong with my Pekin duck's wing?

Just two days ago, I noticed my female pekin duck's wing wasn't working properly (it wouldn't flap and would shake). I'm unsure if it was because she has slight angelwing, or if she has hurt it somehow. When I touched and inspected it, she doesn't seem to show signs of pain, but whenever she strains her wing, it shakes more. I've held her by her torso (I do this to make sure their wings flap correctly) and she tried to flap it, but it just wavers a bit. Her wing doesn't hit the ground like I've seen broken duck wings, but slightly falls limp.

I've read that aggressive, mating males can get their wings out of shape, and my big pekin drake (and females!) were mounting each other!
I've kept her separate from the rest, in fear that she couldn't fly out of their duck pool like they usually do. She's been eating and drinking well, and desperately wants out. When I let her out for a little interaction with the other ducks, she seems to stand alone while the other ducks socialize.
Is it possible that she just hit her wing against something or strained it somehow, rather than having a broken wing?

 

Thanks for responding!
I will try to bandage her wing ASAP!