"Not pursuing this through the appropriate venues—the legal system—simply lets her "get away with it"."
If he expects this to happen again in the future, then it might make sense to pursue a libel case. But if not, and if the premise here is that what she's saying (regardless of whether it's true) is damaging to him, then it makes sense that he'd have to seriously consider whether filing a libel suit against her would really be an effective remedy.
It's unlikely that the objective truth of the matter could ever be definitively proven one way or the other. Therefore, even if he were to win such a suit, the act of defending himself will tend to make him look more guilty and less like a victim. So I think he has little to gain and much to lose from filing suit.
If he expects this to happen again in the future, then it might make sense to pursue a libel case. But if not, and if the premise here is that what she's saying (regardless of whether it's true) is damaging to him, then it makes sense that he'd have to seriously consider whether filing a libel suit against her would really be an effective remedy.
It's unlikely that the objective truth of the matter could ever be definitively proven one way or the other. Therefore, even if he were to win such a suit, the act of defending himself will tend to make him look more guilty and less like a victim. So I think he has little to gain and much to lose from filing suit.