To the girl who slept with my boyfriend:
I hope you know, I could have told your friends but I didn't.
I would have liked some form of apology, but I guess I don't need to wish for something that due to a newly-formed lack of respect for you no longer retains any meaning. I could have told them. The fact that I tell you this is not blackmail - it is my gift to you. I hope you learn to show more respect and caring for the people around you in the future (including yourself) and take responsibility for your actions.
Please have a good life.