Ok, that is worse than I thought it was, I wish I could help walk you through it but the best I can do is a list... 1 don't panic. I know it's hard. But if you panic it will stress out your duck, and stress will make it worse. 2 fill up the bath tub with warm slightly soapy water, NOT HOT WATER...
Maybe put her in the bathtub with some shallow, clean, warm water and let her wound soak for a minute. It'll probably calm her down a bit too. I know that this is scary and stressful but it'll be alright. I've been in this situation a few times before and it usually ends up just fine. You have...
I would rinse the wound with salt water and a little bit of hand sanitizer, then lather the whole thing with a butt ton of ointment or bag balm. I've never had to bandage a dog attack wound but this looks a lot worse than anything my dog had ever done when he was a puppy... he would always stop...