bringin a third person into the relationship

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yesterday I recieved a message on a socialisation site and it sounded like this: the main idea it was that a couple was looking for a girl to spend some wild nights together but also be friends. the message was really long but I was curious to meet the girl so we started talking on messenger. she told me that they had already tried the experience with another girl and that they really enjoyed it. but I was curious...didn't she feel jealous? she said that she didn't...that it was more like a thing he did for her...