If you don't want to be with her just let her go. Don't be a jerk.
Replies 2

Obviously if she is sleeping with other dudes she must not want to be with him either and sounds like they’re both cool with what it is regardless I doubt the poster would take any opinions from a keyboard moral cop who happens to be browsing motherless.com

I don't really understand your logic. How can gasslightning plus blackmail somehow imply she must not want to be with him. If anything, the fact there's blackmail implies she actually wants to be with him.
On other matters, I'm no 'moral cop'. If something turns you on, then enjoy it. I don't care if it's strippers, traps, gay bukkakes, satanic orgies... Please enjoy them. Understand, however, that your right to enjoy a particular kink ends when you're stepping over other people's rights without their consent and affecting their lifes in a way they have not approved of.