I'm utterly confused. Your wife is posting intimate photos on a website, and you haven't seen what she's posting? I guess I don't understand OnlyFans, but I think if I'm in a committed intimate relationship with someone I would be well within bounds to ask them what the fuck they're doing. Also why are they doing it.
OK, I know there are online models who have full support from their spouses. Maybe that's where you'll end up.
But for heaven's sake, talk to her.