What do I do if I am being accused of harassing my ex-husband’s girlfriend?

She claims when I went to my doctor’s office, where she started working a few weeks ago that I threatened to kill her. I did not and there were 20 other people there. She also claims when my mom went to the same doctor and threw papers in her face. When my brother was there he told her stuff. We did none of this and there would be 100's of witnesses if we did. My ex-husband says he was going in to view the tapes and that the police have my plates. I have emails with all these claims from him and her. What should I do now? Her lawyer contacted me last night and also said I slashed her tires. I live 2 hours away and have no idea where she lives and they say there is video on that too.