>Poker
The traditional solution for this is to pull out your big iron and deal with the perpetrator. Not much has changed in the last 140-150 years, except in the Vegas casinos, where the casino bosses will take you to a back room, and beat the shit out of you.
>Relationship
Generally, break up with them, and don't look back. Women are less faithful than us men, despite what the media says. This is also why we should be EXTREMELY SLOW to get married, if at all.
>If she cheats on you once
You can choose to stay with her, because people do fuck up. Don't trust that she'll cut contacts with whatever helped her fuck up, but do verify it. This may require some extra effort on your part, like moving the two of you away or something. If it's a genuine fuck up, then she'll go out of her way to prove that she's being loyal.
>If you believe that you are supposed to stay with her after two cheating incidents
Then you will first receive divinely-given information telling you to do so, and then another source or two confirming this. Then you get to do some kind of monitoring of her, and she should have restricted freedom, as well as verify that she has cut ties with whatever that helped her fuck up. This kind of fuck up usually has to do with some kind of emotional problem or trauma that you were not previously aware of. She'll eventually re-earn your trust. But she'll also get to live with the idea that she permanently damanged your relationship. And in the next life, she'll find out that you stayed with her because of loyalty to a higher cause, not love for her. THIS IS RARE TODAY.
>Orders received to stay with someone no matter how many cheating incidents have occurred
There is DAMN NEAR INFINITY RARE. You will literally be told to stay by divinely-given information, and it will be confirmed via dreams, and several other divine appolntments. There are a literal handful of people on earth that are required to stay with such a partner, but that means there is something way greater going on that depends on such a dedication. This is a difficult path, and few have ever walked it in all of humanity's history. But it means that the partner is important and will need some emotional help to do what they were appointed to do in this life. Lots of people love stupid shit in this life, and it falls onto a very few to help certain important ones to get their job done, despite them loving stupid shit. Again, this is DAMN NEAR INFINITY RARE, and I see literally zero people on this board (from my POV) that are on this path.