Well there are a few things you can do to troubleshoot her...
You can do a thermometer reading. Is it running off normal temperature? (Won't be easy since ducks don't like being held much.) You may have to also compare that temperature to others you have; I think duck temp average is around 107.5? I'm not an expert.
Try to find out right away if she's eating, drinking, and pooping. That will let you know if she's hanging in there.
Then you'll have to probably try to just keep an eye on her and keep her separate from the others. (Which won't be easy because they thrive off knowing the others are near.) Maybe you can pick another duck to be in isolation with her that is less energetic also? Not sure if this is good or not yet?)
If it were a dog or cat they'd put her on an IV for a few days, but I don't know if ducks would even do let you do that without trying to scratch it out, or rip it out when they clean themselves.
With ibuprofen you've got to have the dosage based on her weight, which is way less than a human. If you give her too much it could be a lot of trouble. You might be able to search on the net for a chart based on weight for this? (I don't know.)
While watching her try to recover you'll have to watch for infection and abscesses. (I don't know if ducks get abscesses much, but cats and dogs sometimes do.) Is the smell in the wounds increasing or decreasing is what you can ask yourself. (Yeah, I know ducks smell even when healthy.) The vets sometimes spray this yellow spray on wounds for cows, sheep, dogs, cats that helps with stuff but I forgot what its called. And that was a long time ago so things might be different. And that might not be good also because ducks are sensitive to chemicals with a lower body weight and they also rub their beaks and mouths all over everything.)
If the neck injury is severe enough, she may need help eating and drinking.
While healing up, you would want to avoid solid foods and make the foods stuff that's easy to swallow and pass through like liquefied gruel type of foods.