I find it a bit ironic that you think you need a religious girl to find someone that won't cheat on you. There's this girl I know really well, who when we talked about the idea of polyamoury, had a very strong negative emotional reaction to it. On some level, I don't think she even understands why people aren't satisfied with a single person filling one's romantic/sexual needs. Similarly, I have no trouble imagining you dating a deeply religious girl who cheats on you in some moment of weakness. Religion won't get rid of a desire to cheat; it will only (maybe) change how one reacts to that desire. The only difference between religious people and non-religious people is a belief system of some sort. At the end of the day, people are people with different needs and desires. Religion might change how they react to their needs and desires, but doesn't change them. A girl who will get bored in a committed relationship will still get bored if she's strongly religious. Also, people aren't food. If I go after a married girl, and she sleeps with me, and then ends up getting divorced because she cheated, I'm not entirely to blame for the divorce. She is a thinking, human being who chose to cheat on her husband, not some prize I stole from a museum. In this hypothetical scenario, she still chose to cheat, even if I initiated every piece of the cheating relationship, she's still at fault for reciprocating. (Note: I said that in this scenario I'm not entirely to blame. I'm still partially to blame. Significantly.)