I have a rescue dog who is wonderful in every way except one

Petrina,
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Thanks for the additional information. It is helpful. It sounds like she has a touch of leash aggression toward other dogs. Often this starts when an owner is unsure of a dog's reaction to other dogs and they are on a leash. The owner tenses up or pulls their dog back to them. The dog picks up on the fact that the owner is a bit worried and figures they are worried about the approaching dog. They then react in various manners. Some will try to flee, others will act aggressive toward the dog lunging and or barking. If you also try and reassure a dog reacting like this, it actually is positive reinforcement and will encourage the behavior the next time.
Now I know that often you are not aware of the approaching dog, but if this is an ongoing issue, it is now a learned behavior. So she will need to be taught what behavior you expect in those situations.
The first thing I would work on is obedience training even though she is very good. It helps her see you as the boss and leader which she may already view you as such, but it also helps finish her obedience work and then she will listen the first time, every time to commands. The following site is helpful for teaching you how to train your dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
http://www.schutzhund-training.com/training_theory.html
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Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
http://www.pets.ca/articles/article-dog_nilf.htm
You will try your best to keep a loose lead and not tense up regardless of the situation. Try to ignore bad behavior if at all possible. Perhaps you can set up a cafe like area and enlist someone who has a dog to help with training. Set up the cafe area with some friends, etc and have the "strange dog" walk past your table at a distance that you think will not trigger your dog to react. When she doesn't react, reward her with calm praise and a tasty treat like a hot dog slice or liver sliver. By now your dog knows you have the treats and should be a bit more focused on you rather than other things.
Gradually have the other person and dog move past at a close distance, rewarding the desired behavior of ignoring them. If your dog should react, give a short tug to break her concentration and a firm low toned NO and repeat the exercise with the dog a little further away again. Once she is not reacting to that dog which may take weeks of daily training, switch to a different dog starting at a distance. With each successive dog, the training should go faster until she learns that you want her to lay quietly regardless of dogs and people approaching.
Now this does require that you keep an eye out for aggressive acting dogs and ask the owners if they will move their dog away or pass at a lttle distance from you. Most owners of dogs are willing to do this. I also want to give you a site that goes over non verbal dog body language so you can tell if an approaching dog is dominant or aggressive before it ever reaches you. If you are pretty confident that a dog is not going to be a problem based on body language, you will be calmer and the dog should be calmer as well.
http://www.apdt.com/petowners/park/body-language/
http://www.pawsacrossamerica.com/interpret.html
http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/canine-body-language
I hope this information is helpful to you and you are satisfied with my response. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have .
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