Please help me with my psycho ex girlfriend!?

Okay, so my ex broke up with me and moved out on her own. Not that I had a problem with it, Ive been trying to get rid of her for years, but it has never been simple. Everytime I have tried to break up with her, she has blackmailed me into taking her back. We have two kids together, and honestly, I have no desire to see them because I know it would involve seeing her. That is how bad I never want to see or have anything to do with her again. I am willing to give up my children to never come in contact with her again. Anyways, she finally had enough of me and left, broke up with me and moved out. Relief. Finally, I was able to move on with my life. Wrong. Just recently, she started calling my workplace and my friends and is telling everyone that she has "pictures" of bruises that I left on her when I supposedly "beat her". I have never laid my hands on her. Never. But, she keeps telling everyone that she is going to call the cops and that she is going to put me in jail because I beat her. I know that I have not hit her, but who will they believe if she does call the police? Is there anyway that I can get around this? Is there anything that she can really do or is she just bluffing to try to blackmail me into taking her back? I know I never touched her, but I also know that law enforcement will take the word of a single mother before the word of the ex father. Please, Im asking for any advice that I can get from anyone. Anyone who has ever been in this situation or from anyone who knows the legal system. Or just anyone who could help. Please.