Ending a Friendship When the Other Person Does Not Want to

Hello everyone:

i have a friend that has caused me and my family a lot of turmoil during our 10 month friendship. At first she was fun and not too aggressive. She and my husband had an disagreement over her dog trying to attack him back in january. I overlooked this and continued our friendship although my husband warned me that she will snap on you. Then our kids started dating (my daughter - her son). That is when things really went downhill. My daughter would have a minor dispute with her son and she would be flying up my driveway to chew her out. It was insane - kids need to learn how to fight their own battles. By the end of the school year in may my daughter had a very big falling out with her and her son. This is when I decided to end the relationship. I did not phone her or return her emails. All was well for four months and then on the day the kids returned to school, she was calling and leaving me messages. I finally responded to her email telling her that I prefer for things to remain the way they are as everything happens for a reason. That was not good enough for her. So I told her that there are things that have happened between us that I can not ignore and that I needed to stay focused on my family and work. That did not fly either as she is now writing to me (at work and home) stating that she does not understand why I feel this way, etc. I will see this woman at school events and we live in a very small town. How would you recommend I handle this situation? I have only known her for a year and others in our area have also had bad experiences with her, mostly over her kids. I believe that she is very vindictive and spiteful. I also believe that she will not take rejection very well. She is definitely confrontational, she likes to fight and her temper flies off the handle when she has her mind stuck on something or on the defense. Thank you very much for your help with this - I truly appreciate it.