Ex-Wife making false allegations

Throwaway account: Basically, I got my high school girlfriend pregnant, joined the Military, married her, went overseas, we didn’t workout, we got divorced, haven’t been cordial since. We got into a big argument recently and she told me that I slapped her during one of her OB appointments in a doctors office while she was pregnant. This was the first time I ever heard of this allegation and it was supposedly 7 years ago. I have no idea why she said that but that’s a very strong allegation. Recently, she’s been posting on her Instagram stories with cryptic messages like “you won’t get away with this forever, end violence against women.”

My question is, if she ever decided to go public about this, how far could it even go? It never happened so there’s absolutely zero evidence and the claim is from 7 years ago. I’m just trying to be prepared considering she’s volatile. Would I be able to sue her?