Savage Love

I'm a 27-year-old man in a two-year relationship with a 26-year-old woman. My last partner cheated and lied and did some unforgivable things. Our breakup unearthed a kink. After I found out about her cheating, I got extremely turned on thinking about it. I never told her.
Enter my next girlfriend. We were together a few months before I brought up my kink. She was very accommodating, and after some months, she admitted that it was something she wanted to try in real life. I said I was OK with it as long as I had the option to pursue other partners as well. We agreed on some rules and gave it a shot. She set up a date through OKCupid and had sex with someone; I hooked up with an ex. Everything seemed to be turning out great. Then two weeks later, she got drunk and told me she had seen the OKCupid guy again without asking. I was so upset, I nearly broke up with her. Having the guidelines ignored felt like a betrayal.
Are we going through the normal trip-ups of a newly open relationship? Or are these lies an indication that she can't be trusted? I feel like it might be hard to find someone else who is into my kink and maybe we're just having a hard time navigating polyamory. I love my partner, and I want to make this cuckolding thing work if we can. Suck it up or break it off?
Confused Upon Cheating Kink

First things first, CUCK: Polyamorous relationships and open relationships are two different things. Some poly relationships are open, but many poly relationships are closed – that is, three people (or more) are involved with each other exclusively, i.e., no randoms, no romancing potential fourths, fifths or sixths. The reverse is also true: Not all open relationships are poly. Two people in an open relationship may allow fucking around with other people with the understanding that there will be no dating or falling in love with anyone else.
And then there's cuckolding. The whole "cuckolding thing" is about the female half of a heterosexual couple breaking the rules and then rubbing her partner's nose in the evidence of her cheating. Cuckolding is eroticized betrayal, and you spent months fantasizing with your girlfriend about being betrayed. But when it came time to turn your fantasies into reality, you laid out the rules for what sounds like a fairly standard open-not-poly relationship: She could fuck other people and so could you. Once again, I'm confused: The cuckold in a "cuckolding thing" typically doesn't get to fuck around. He gets fucked around on.
If your discussions with your girlfriend were as confusing as your letter, it's possible that she was likewise confused. It's possible that she thought the rules applied to you and not to her. It's possible that she figured she was free to break the rules because betrayal turned you on. Now she knows that betrayal turns you on as a fantasy and not a reality.
Seeing as you love her and want to make this work, and seeing as girlfriends who are open to cuckolding are hard to come by, I think you should give her the benefit of the doubt. Time will tell if she's an honest "cheater" who can be trusted or a lying cheater who must be dumped.

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