First, get a no pull harness. That will stop her straining and pulling at the end of the leash because it's uncomfortable under the arms if they pull.
Next, change directions, a few steps, and make your dog sit with it's back to anything it's over reacting to. Repete till dog gets the idea that calm looking is ok, and barking lunging, circling on the lead etc, doesn't get them the response they want.
Take treats while walking , kitty kibble usually is interesting enough and easy to carry, and give tiny treats when they act calm or sit when told.
Be sure your dog is getting plenty of mental and physical exercise to keep healthy and mentally/emotionally balanced. Maybe find an agility course and trainer that you could work with, or teach your dog to search for things you hide around the house and yard.
Enjoy your little dog, sounds like a smart and eager one.
35 years training, raising, breeding, showing, rescuing, boarding, dogs, cats, horses, guinea pigs , Sulcatas, Bearded Dragons, growing rare plants, ex Nurse, ex EMT. 12 Grandchildren. Manage 150 dog Pet Resort.