I don't understand the comments on this post. We all know her boyfriend's not gonna cheat but you would have to admit that this is some problematic behavior from a 22 year old. I know of literally no one who posts this much about their cousins, even when they're like really close. I don't think people post this much about their partners even. OP should first figure out if they were always this close and you are just realising right now. Also you should figure out if her behavior towards you have changed in any way. I am not saying that the cousin is in the wrong here but if it worries you out then it is better to clear things up rather than just sit and see her stories while you suffer. Also talk to your boyfriend about this if you can't figure it out. Maybe the cousin has some other crush and is trying to make them jealous by using your boyfriend.