When there is just a tiny bit of snow, sweep it with a broom. More, shovel. When the chickens can only see snow because you can't get down to ground spread hay or leaves . It helps to have a sheltered area where the snow is kept away - maybe a picnic table or plywood up on blocks or a roof of something....and the water and feed can go there. I keep feed outside too.
Except on super cold days, then I might bring some feed in side. Or when I have some separated for some reason.
Hey the BO with the bum legs actually stood for a good period of time. So maybe she is getting stronger. I tell you, it is a pita to clean off frozen poop balls from her rear feathers.