The summer before 10th grade, when I was 15, I made out with a guy my best friend had gotten with. It was a mistake that to this day I still apologize for, even though my friend forgave me within a week of the event. Yet, I will never forget the look of hurt in her eyes, the way her face fell, and how she locked herself in the bathroom for three hours after she saw us.
Years later, I still react the same way when I hear a friend of mine say they have gotten with/slept with/made out with a guy I've been talking with. I freak out that they may be upset, so I start apologizing endlessly. That's followed by bashing said boy, and ending with a “If you care at all tell me and I won't speak to him again." But you know, I can honestly say turning to another friend of mine to bitch about a guy can bring us closer. We have this mutually understanding and knowledge and we can honestly say, “I know how you feel" when the other is complaining. Maybe this whole Eskimo sister thing is actually a good thing in disguised.
Nothing really bonds a girl like a good b*tch session. Something about a mutual hatred for the same thing (or in this case person) brings girls closer. Of course if you see your ex (boyfriend, hook up, etc) with a new girl, your initial reaction is to hate her. But, if the guy does to her whatever he did to you to end things, there's a new bond there. You both know exactly how it feels, you understand each other's pain, you both mutually agree that his body that you once swooned over just actually makes him a gym-obsessed meathead.
Eskimo sisters need to stick together. You have both been there done that and whether or not this guy was the love of your life or a one-night stand you will pretend never happened for years to come. You have a different understanding of what this girl has been through and you know exactly how she feels. So instead of hating the girl your ex boy toy has moved on to, maybe look at it as a future best friend. Because lets be honest, when this guy royally screws up (which he will) you'll finally have someone new to b*tch with. I mean, it is called Eskimo SISTERS for a reason.