I breed, raise, and train herding Collies, and have trialed most of my dogs competitively, and have titled them. All but my two youngster dogs (I have 7 dogs total) also have their CGC and their TDI certification. My oldest dog (an Australian Shepherd, BTW) was also extensively competed in obedience, agility, and dabbled in flyball.
I also keep a flock of free range chickens that are loose on my property during daylight hours.
My dogs are NOT loose on the property. They are worth too much to me as beloved pets (as well as financially) to risk them being injured, shot by a farmer neighbor, hit by a car, or wander off to be bred by the neighbor's mastiff. I live in a very rural area too, but protection of my dogs is a priority to me.
It is one of my dog's job in particular to make sure the chickens are up in the coop at night and she knows how to herd them appropriately. All my herding dogs are actually started on chickens first, before moving up to larger livestock.
I agree with Barry in the sense that Claire's instinct to herd and chase is inborn, and is not going to go away. You can't expect her to just not do it. It's in her blood. That is why your better choice is to teach her to have an appropriate outlet for that behavior, and the guidance of a good instructor who knows herding dogs. It does not cost a lot to have just one particular issue addressed. And being in a very rural area works to your benefit in this case - good herding/stockdog instructors rarely ARE in cities, as most people frown on a herd of sheep in the back yard.
The upside is, you could not only have a dog not posing a danger to your chickens, but she could actually be a useful and valuable tool around the place if you bothered to put the effort into having her trained correctly. A good stockdog is incredibly helpful in so many ways.
That being said - I am of the personal opinion that no dog, EVER, should be allowed off leash, outside of a fenced yard - unless their recall is absolutely 100%.