Why is my ex’s current girlfriend attacking me with false accusations when I’ve moved on and never bothered her?

I genuinely need advice because I don’t understand why this is happening.

My ex and I were together for four years. During the breakup, I was already going through one of the worst periods of my life. My grandparent passed away, my father was suffering from a heart attack, and I was also dealing with the pain of being cheated on and emotionally destroyed. I spent around six months depressed and struggling to function.

Eventually, I slowly started rebuilding my life. I began working, helping my family, and trying to move forward. I was finally starting to live again after everything I had been through.

My ex moved on and is now dating someone else. I never tried to interfere in their relationship. I have been trying to heal and move forward with my own life.

But now his current girlfriend has started posting accusations about me that I believe are completely false. She is trying to portray me negatively and damage my name, even though I have not been contacting her or trying to disturb their relationship.

What confuses me the most is: why?

Why would someone who is currently in a relationship with my ex still be so focused on attacking me? Why spread accusations about someone who is no longer involved in your life?

I have already survived the cheating, the heartbreak, depression, family trauma, and the process of rebuilding myself. I don't understand why I am still being dragged into their lives.

I am not trying to start a public fight or attack anyone back. I just want honest advice:

How should I respond when someone posts false accusations about me online? Should I defend myself, ignore it completely, or keep evidence in case the situation escalates?

Has anyone experienced something similar? Why do you think she might be doing this, and what is the healthiest way for me to handle it without getting pulled back into their drama?