Her (now former) boss is a county sheriff. No threat of criminal enforcement? Evidently not: he says it's a law he doesn't enforce. It's more of a "moral" issue with him; he prefers not to employ
So it's a 200-year-old law that's rarely and unevenly enforced,* it's on dubious ground since Lawrence v. Texas, and it touches the lives of some 144,000 North Carolina couples. Doesn't seem like a baseless claim to me.
* According to one report, a federal magistrate judge in Charlotte "regularly asks defendants whether their living arrangements violate the cohabitation ban. [The judge] has refused to release violators unless they promise to comply."