How can I protect my children from their father's girlfriend.

My children are 15 and 10. My ex husband and I get along well. However, his girlfriend and I do not associate at all. She badgers my children with outrageous lies about me. For example: she has made criminal allegations such as I broke into her house and kidnapped her children. She has told them that I have tried to kill my youngest when he was little. She has told my youngest that the reason he has ADD is because I shook him as a baby. She has told them that she knows that I let people walk around naked in my house. She took food out of the garbage and made my youngest eat it! And the list goes on. My boys love there dad and want to see their dad and their little sisters so they keep subjecting themselves to this mental torment, but they do not want to be around her. What can I do. I don't ever want to keep them from their dad but I can't sit back and watch them be torn apart by this mental and emotional abuse! What are my legal rights in the state of NY in Chautauqua county?