How to deal with online harassment/defamation with my employer?

My ex-girlfriend who (I thought) I was still friends with has been making out of context defamatory posts about me on various incel subreddits. I'm a fairly high-ranking employee at a big corporation. When I confronted her about this, she threatened to post the same content to my employer's social media channels, along with a made up story about how I subjected her to sexual and emotional abuse. Her stated goal was to get me fired from my job. I took screenshots where she discusses her plan.

Although it has been a year since we were last together, she initiated not one, but two relationships with me. She wanted to get back together even though I was already in another relationship, which she insisted I end, because of "how pure" our first relationship was (there were no allegations of abuse). I never treated her with anything but the utmost respect. I have lots of old texts to back this up.

Is a restraining order a good way to proceed in this situation? I used to live in another state, but I recently moved here for this job. Would the order prevent her from contacting my employer across state lines? I am assuming her other online harassment is a lost cause.