Welcome to BYC. So sorry to hear about your Pekin.
One problem everyone will eventually encounter when raising ducks, is leg problems, especially these minor injuries they're simply inevitable at times. Whenever you go out to the park, or simply take a nature walk and see ducks, where do you always see them (?) water of course. Rarely do you actually see them on land, so given the fact that us owners are keeping them on land for longer then they're intended to be, and creating heavyweight breeds like Pekins, leg problems will eventually happen because they're not anatomically designed to walk on land for long periods of time.
That said, putting a high emphasis on providing them with deep water to play in, and keeping their pen area softly padded, free of things they may trip on, will in the long-run prevent some of these problems from happening.
What you've done now is perfect, we don't want her walking on the legs too much right now and further injuring them, we also don't want to keep her like a vegetable, so letting her move those legs in a water source a couple of times a day will also keep her hygiene up, as well as reduce some of the inflammation in her leg.
From what I've seen, most vets will recommend starting the bird on an NSAID, to reduce any pain, or inflammation going on. They specifically tend to use Meloxicam (Metacam) most often, but if you don't have that on hand there are several NSAID you might already have in your house.
One option would be to give her some baby aspirin and dissolve one 325mg tablet into 250ml of drinking water. Or, you could use Ibuprofen, the dosage is 5-10mg/kg two-three times a day. Or if using the liquid ( 100mg per five ML/ 20mg per ml) you can administer 0.11ml per pound of bodyweight. The final option, would to be use DMSO gel (Dimethyl sulfoxide) to where you deem the injury to be. Simply, dilute the gel down halfway with water, and apply it to the area wearing gloves, and repeat as needed. Links to the products mentioned below.
Two last things I'd like to mention regarding the NSAID's, one being, there is little research surrounding using human NSAIDS on birds, short-term is appears fairly safe, but there may be side effects such as GI tract upset if you continue to use them longer the two weeks. Also, the NSAID will mask a lot of the pain, so don't let her out of her pen too soon, or she will likely re-injure the leg before its completely better.
https://www.tractorsupply.com/tsc/product/valhoma-dmso-99-pure-gel-formula-1-lb
https://www.walmart.com/ip/Equate-Ibuprofen-Coated-Tablets-200mg-100-Count/10325055
https://www.walgreens.com/q/baby+aspirin