Put duct tape or a saddle over the bare patch on her back if that is picked. The vent you can't do anything about, really... separate her with a cage (we use a dog cage) in the coop so she isn't lonely but the other hens can't pick at her. And wait until the feathers grow back (luckily with a...
I'd guess that the molting presented nice fluffy underfeathers and bare skin, and the other bored hens said, "Oh, look! Yum!" and that started feather picking.
Even if there's no rooster, feather picking still happens. Especially in winter when they're bored. Unfortunately, it even happens in our small flock of hens.