Good point, bumblefoot would not spread. The other option of mites seems logical especially since she was exposed to it by the rooster. Poor girl! Mites can be hard to treat. I’m sorry I’m not familiar with Fauvas to even give you tips on it. Hopefully, some long term chicken keepers will chime in!
Welcome to chicken keeping! It’s an enjoyable adventure. We use sand as well (in our run). It is the best alternative for us! Our girls love it and enjoy taking dust baths, scratching, and digging holes. Realistically there are not going to be many bugs in the run or coop. At least I wouldn’t...
We have a small above ground coop. It has been a fantastic choice for our small flock. It is predator resistant. It has a resin floor that allows poop to fall through to a drawer. It takes about 5 minutes to clean the coop. Because we live in a cold Northern climate it also allows the girls a...
It sure looks like a bad case of bumblefoot to me. This link has some very helpful info. Good luck with your girl!
https://www.fresheggsdaily.com/2012/03/bumblefoot.html