Can I file harrment charges, slander or libel against someone?

I have a dog rescue. Some nutcase has come out of the woodwork and started calling me a sicko dog hoarder who abuses their animals, made bogus appointments at our shelter and even turned me in to the animal control! I have no idea who she is or why she is doing this. No one takes better care of the animals than we do. We spent most of our retirement money setting up this shelter, making in warm and comfy for the dogs, putting in a fortune in the best kennels and fencing so they could play outside as much as they wanted, Inside we keep it clean and warm, air conditioned in the summer, give them love, complete vetting, we've taken in sick and abused animals and gotten them well and taught them to trust again. All with our own money! Then this weirdo appears, accuses us of starving and mistreating the dogs and turns us in to the local animal control, who came out to inspect us and wound up giving us a gold star rating! She keeps haring me via email and probably out in public as well. I tracked her down on myspace and she's a damn pit bull breeder! How ironic! I'm the only rescue in the area who will still save a pit bull! Can I do anything about her? I found out who she is..can I press harment charges or slander or libel? I need some ammo so she'll stop all this. We've built up a good reputation and don't want her ruining it.