You might like this thread
http://www.dobermantalk.com/showthread.php?t=725 since there is a lot of good information about this topic that seems to relate to your situation as well. Make sure and watch how you act when other dogs come around, you could be giving her cues you aren't even aware that you are giving. When you tense up, expecting an ugly scene, that sends signals.
This is taken from that thread: Whenever we would walk past another dog or person (he wanted to meet everything) I would make him focus on me, using the treat. At first I had to wave the treat in front of his nose, talk to him and feed the treats to him in rapid succession. I would tell him what a good boy he was. Communication is important of what you want. You have to let the dog know what is the proper response. It is more effective and better to give treats, feasible commands, and praise, than to say no and jerk the leash. I would keep the leash tightly in my hand, (not too tight with a little bit of slack), enough to not let him be able to lunge toward the other dog/person or get very close to them. We would keep on walking by while I was feeding him and talking to him, it was not a moment to sit and wait for what happens. Sometimes he would be required to sit or look at me in the eye when we had been doing the treat thing for a while. Eventually when he saw another dog or person he would start looking towards me for a treat or command and would be rewarded for that behavior. He needed me to help him learn what to do and he enjoyed the extra treats, extra walks, and extra time spent with him. It was a positive experience. We took walks in different places all the time so he could check out new environments and build his confidence at the same time.
Make sure the treats are really high value treats, something very smelly that she really loves and wants to eat. Help her learn to focus on your during your outings and make other dogs a non-issue. Be proactive.
This behavior modification approach did two things, one it helped this dog learn that other dogs meant something great, yummy treats. Dogs = delicious treats from owner.
Two, it helped train him to focus on me during distractions.
Here is a good place for reading :
http://www.flyingdogpress.com/articles.html
There are certain obedience classes at some clubs that deal with young dogs like this. Ask around at obedience clubs in your area. Tell them the whole story about your girl and see what they recommend. You are very smart to want to deal with this now in a puppy and not wait until she becomes an adult. Good luck