I'm not interested. If I want to see sex on camera, I'll watch porn, not some rando banging a chick I fucked a few times.
The more important thing is I want nothing to do with that dude, or anyone who does that sort of shit. If somehow he's selling it on her behalf or they've got some revenue sharing agreement, I'm still not interested for the above reason but I won't hold a bad opinion of the dude per se. Otherwise, I make it a point not to get involved with people who are fucking over or even just talking about people they used to be involved with beyond casual mentions in passing conversation. It says enough about their character for me to know I'm not interested in doing business or being friends.
It probably means I want nothing to do with that chick either, even though the circumstance in question may be no direct fault of her own. Like Ibb said, I'd probably give her the heads up about it but I'd limit my further interactions.