This has already been going on for a couple of weeks? Oh, I was thinking this was something that just happened. I might rule out sprain if she hasn't improved any. Would you know if it was swelling worst than it is now? (It looked almost bruised too in that spot, making me think sprain.) Or, do...
Unfortunately, I don’t know what type of antibiotic to use either.
On a side note, can the duck bend its leg on its own? It looks like it might be a minor sprain. I suggest putting her on a stable, flat surface to minimize possible stumbling blocks. (Keeping her in a kennel with the tray or...