Do I Truly Have the Right !

I have a neibor that constantly stops on my road and cusses at us and threatens to kill my dog. She also brings rocks with her and throws them at my dog (yellow lab). My kids are often outside and wittness this. She has a long list of violent affences with the law including beatting her childen, sister and girl freind. Resently it has gotten worse so I called the sherifes office for help. The sherife said he would talk to her before it escalates farther. Two days later I went away to get married, the sherif had not called me back at all. A couple of days after I  got home from my honymoon My neigbor and her neice on the back drove up on a four wheeler and stopped in my driveway, turned off the motor and pointed to my dog around 60 ft away and her dog took off after my dog. In the four years she has been here she had never brout her dog with her.  I was on my pourch talking to another neibor at this time, she did not see us. We were 160ft from her and her neice. I did not want to get in the middle of a dog fight so I went into the house to get my shot gun. My husband came out with me. I felt the noise would scare the dog. But if it attacked my dog I would shoot it. I remaned on my pouch and after several minets she noticed us. She did not call the dog but had the 12yr girl get off of the four wheeler and walk over and get the dog by the collor and walked it back to the four wheeler and they left. I called the sherif.  The DA is pressing charges against me,  two counts felone menicing. I pointed the shot gun straight up the hole time. I never verbally threatened them. I never left my porch 16ft away from them. The DA said the law is black and white, I had a gun and they felt threatend. He pressed charges against me. Can I not protect my dog from another dog?