.... I can't believe that whatever grabbed that chicken did so that close to a dog going nuts. My girls will be kept contained for at least a few days as I know it will be back. Ultimately you do the best you can. I'm very sorry to hear about your girl.
Most predators are very clever. They watch and learn. A predator watching your property will have learned exactly how far that dog can reach and will stay just outside the zone, probably very calmly and methodically going about his business even as the dog was going nuts.