It should be noted that this just goes for western sites, which have developed a pretty cuck centric definition of NTR. Female POV NTR has always been a thing in Japan, the country where the genre actually originates from. In fact, the majority of japanese NTR hentai has fem MCs.That's just called "cheating" Those stories are quite literally about a girl cheating on her husband/fiancée/boyfriend. Pretty much all websites (including F95) have a separate "cheating" tag, so just search for that (preferably in combination with the "female protagonist" tag if you want that POV).
That's why the term has become pretty useless in discussions on western forums: You have people who straight up don't consider classic NTR stories to be actually NTR, while others consider everything NTR where a female character interacts with another male that's not the MC, and be it in the most casual way.