You might want to go read the thread about dear Hostile Hannah for a bit of insight as to what reinforces this behavior as well. Hannah is doing great. You must remember she is who she is and that she is not making good decisions. That means that you must start making those decisions for her which will build her trust that you are not going to put her in dangerous situations and that she has some rules to follow. That also means that when someone wants to pet her your happy response is "oh, not today, she is in training" and move on. Each time she scares someone off she is going to be quicker to do it the next time so you want to remove that opportunity. This will get you started.
http://www.rottweiler.net/forums/behavior/41919-less-fearful-people-who-have-dogs-them.html