So? She was your ex when she made out with your best friend. I believe the stupid rule of "no dating friends of the ex" was put in place by insecure, hateful people. I would have absolutely no problem if my ex started dating one of my girl friends. He`s my EX, we parted our ways, why should I care who he dates? You people need to learn to let go of the past.

you should get a new bestfriend