[gemy]

Here I agree muzzles do not make dogs angry or dangerous.

My suggestion is to take her to obedience class. She is 4mths old? If so good time to start puppy obedience. Here you learn how to handle your dog, and under the eyes of an experienced trainer. And make sure it is an experienced trainer before you sign up for class; ask questions, ask to observe a couple of classes so that you get a feel for the teacher and the class dynamics there.

Next, you don't mention how often you walk her? Good healthy exercise is so important for not only their physical health but their mental health as well. Take her out as often as you can in a day; even if only 10 minute walks, or 2 20-30 minute walks.