That does look like scaly leg mites. I would treat her by coating her legs in Vaseline, and then covering her legs in gauze and vet wrap so the little chicks don't coat themselves in it when they go under her. Just change it daily and it should clear up. Don't be alarmed if when you unwrap her legs some scales come off with the wrap, this happens because the Vaseline loosens things up and it's normal for them to shed the damaged scales.
The active ingredient in scaly leg protector that i used was citric acid. I would assume that wouldn't be too hard on chicks. I found it not very effective though in treating the leg appearance. I used bag balm on a rooster that had it and the scaly leg protector on a hen because she had chicks and i didnt want them sticky. They were older chicks in my case. The roosters legs healed, but the hens didnt until i used the bag balm. Its very messy, but really softens the leg scales, and they seem to come off easier. The idea mentioned of using a vet wrap is excellent, I wish i had thought of it. There is also wound wrap for humans at the store that sticks to itself only, if you don't have access to the farm or vet store. I treated every day for a few weeks and then tapered off. I would scrub the legs with a toothbrush and apply bag balm. I used diatomaceous earth sprinkled in bedding to try to prevent any spread. I think vaseline and bag balm may be equally effective too, i would use what is more available.
Not only does it look like scaly leg mites it also seems that she has some bumble foot involvement with her left foot. It doesn't take a 55 gallon barrel of product to treat a hens legs, just a thin coat that is reapplied often will do wonders. Don't worry that your biddies will weld themselves together with the Vaseline, Petroleum Jelly, or Bag Bomb. They are much tougher characters than we give them credit for.