I recently read a post on the reddit page /r/offmychest where a married woman said she found out her husband had been sleeping with a seventeen year old girl. Obviously this is a demonstration of betrayal of trust, and she has every right to feel cheated by life.
However, I noticed something odd about the way this woman talked: she seemed to blame the girl for what happened, by calling her a home-wrecker, saying she was a slut, talking about how she'll be worthless and unloved in several years, and more.
I personally have always been bothered when someone cheats on you, and the person who was used in the cheating gets the blame for their actions. Here's why: let's say that Dick and Jane get into an intimate relationship, and during that relationship, they decide to be sexually and romantically exclusive. Now, Dick goes off with Susie instead of Jane. In this interaction, Jane will most likely get angry at Dick for breaking his promise and abusing her trust, but she may also get mad at Susie for facilitating this interaction.
There are two problems with blaming Susie though:
1) Susie didn't break anybody's word or trust. Unlike Dick, who promised not to do something and then did it, Susie has no obligations to Jane whatsoever. Some may argue that everyone has a duty to be a decent person to those around us and such a promise would include not having sex with a taken man. However, such an argument is not quite applicable, because in this case Dick is not breaking a promise made by society on his behalf, he is breaking his own promise, from his own mouth, utilizing the trust he built up with Jane. Susie didn't manipulate or abuse anyone's trust or close connection in order to achieve her goals. If you believe Susie is to blame in this situation, it would have to be in comparison to Dick at a 70:30 ratio or something.
2) You do not know how this situation played out from Susie's eyes. From Jane's perspective, she is Dick's "real", most likely longterm girlfriend, and Susie is just an "on-the-side" "slut". However, for all Jane knows Dick's been playing both of them for the same length of time, and Susie is as equally astonished by this revelation. In hearing that Dick and Susie were having sex that violated your relationship, she assumes Susie knew it was hers and took it from her, when in actuality Susie was as surprised as you.
I should also reaffirm that the "Susie" in our story was younger than eighteen, when the "Dick" was older than past his mid-twenties. While a teenager is somewhat of an adult, they do not have the same foresight or experience which allow them to make better decisions; saying the event was Susie's fault is like saying a three year old is at fault for touching the hot stove. The fully grown adult is more aware of their surroundings and thus has more culpability for their actions. If one is to claim that both of these individuals are on equal footing in terms of responsibility, you are most likely speaking out from a position of emotional bias.
Please, remember to keep interpersonal complications in perspective, life isn't always as obvious as it seems to be.