One - I get that you are in the country and you want to be able to let your dogs loose. I don't agree with it, but addressing your issue based on that point -
Firstly, even if the ultimate goal is for her to be trustworthy loose, right now she is NOT. She has shown you that. So the first commitment has to be to make sure, until she IS trained to leave the chickens alone, that she is not left with them unattended.
You have a dog with herding blood, she is just following her nature. Any dog is going to be inclined to have interest in chickens, but a herding dog in particular is going to have that overpowering chase instinct so when the chickens run, her instincts over-ride just about anything else.
And just to make things a little harder on the poor pup, her other side of the bloodlines (the brittany) is a very active hunting dog who also has a very strong chase instinct. A breed that generally has a reputation as cat killers, as well. So she is fighting against a lot of history there. All things to take into consideration, in the future, when selecting a dog you intend to have around your livestock.
Your very best bet in this case would to get involved with a herding trainer that can give you a couple sessions with your dog to help her learn some boundaries when it comes to livestock. Most stockdog trainers are willing to address issues like this pretty cheaply. And you may find you have a sport/hobby you enjoy with your dog, in the process. This is the best advice I can give you, but I suspect it will be out of the question.
Your option, if you are not willing to contact a trainer, is, as coffee suggested, keeping the dog on leash and working around the chickens - correct her (not beat her, or hit her, or kick her, or tie rotting carcasses to her) when her attention is fixated on the chickens and reward her attention on you.
None of this can be done in a weeks time. If keeping her leashed and supervised until you HAVE had time to properly train her (several weeks to months, as Coffee mentioned) is not possible for you, then I suggest finding a better suited home for her now is probably what you should go ahead and do.
Just as a final curiosity - your dog is a double dilute. Double dilutes are very, very often deaf. Are you absolutely, 100% certain she can hear?
Last edited by Indyhorse; 07-02-2011 at 10:40 AM.