Adopted a dog recovering from illness -- follow up questions
St. Hubert's offers a special class for dogs who are reactive on leash and/or towards other dogs. It's called Feisty Fidos, and it made a world of difference for our rescue pup whose behavior sounds much like your sweet dog's. You can call to ask them how to enroll. We also worked with a local dog trainer before we could get into the class and were very impressed and appreciative of her work with our pup: Sara Matters of Training Matters (973-699-3088) -- she also has a Facebook page.
Agree with cupoftea. Redirection, BEFORE your dog reacts to others, usually works best. So you have to be constantly vigilant. Also agree with eliz that your dog should be evaluated by St. H's and based on that, consider enrolling her in a Feisty Fido program or, maybe, with proper handling, she may be able to integrate into a basic obedience class. The important thing is to get this taken care of immediately so that it doesn't continue ,and hinder your dog owning experience.
This blog post by Patricia McConnell, Ph.D, gives some insight and tips on leash reactivity.
http://www.patriciamcconnell.com/theotherendoftheleash/dog-dog-reactivity-ii-the-basics
Dogs reacting on leash is common. I have two dogs so it's near impossible but for the dog that has many triggers I tried to preempt as many as possible by distracting him by asking him to follow commands and lots of high value treats (the grosser they are to you the more the dog loves them). He's now so much better around cars and rarely reacts to runners. We use someone who keeps our dogs at her house. I'll pm you.