Tree Branches and a spiteful neighbor

From reading the many queries on this site, I no longer feel alone in the world of being victimized by a poor neighbor. Two years ago, the perfect neighbors moved out from the house next door and a neighbor from hell moved in. The woman who bought the property was working for me at the time and I also considered her a friend. However, she began to treat my property as her own. When I would get up in the morning and look out into my back yard, she would often be wandering around in the yard. She lets her pets use the neighborhood as a toilet including our yards, despite the fact that our community has a leash law. I also began noticing that there was an abnormal amount of tree branches piled along the property line. At first, I chalked this up to her quirkiness and just picked them up myself. But overtime, a feud has grown.

One day, I came home from work to find branches piled high against my front door with a threatening note that the branches come from my trees (which may be true . However, we live in the windiest state in the country and leaves and branches from neighboring trees landing in ones yard are not uncommon) and that I need to keep them there and that I should contact an attorney to verify that. I called the Sheriff and they talked to her about the incident and told her stop but the branches keep coming back and they really don't want to do anything about it.

On top of it all, I have two young children, one eight and one two. She is constantly verbally assaulting them and reporting the older one for things he hasn't done. She tells him that he is going to be a serial killer. Most recently she reported him for shooting out garage windows with his bb gun. I've agreed to pay for the windows but other neighbors think that she broke the windows herself when she was mowing her lawn (Something that only happens twice a year and she could easily have thrown something up without seeing it in the overgrowth). Plus, the windows were broken out over a month ago and she waited until we were on vacation to report it.

I need to find some legal precedence. So far I've tried to look the other way (with the exception of losing my temper with her and yelling back at her when she's been picking on my kids) and hope the situation will just work itself out. But this woman has a personal grudge and I suspect a mental problem. What can I do?