Dear ...
I am struggling to find the words to express how much I hurt right now. Actually, I don’t even think there are words that can describe the depth of the pain and betrayal I feel. When you told me that our friendship meant more to you that sleeping with my ex, I actually believed you. And now I wonder how I could have ever been so naïve to think that you really meant it.
Was I not hurting enough by the break up between me and __(Ex’s Name)__, that you both thought you ought to stick it to me thoroughly? Never mind how heartless __(Ex’s Name)__ is, but how could you too, __(Friend’s Name)__, someone who professed to be my best friend, do this to me? And then have the audacity to look me in the eye and blatantly lie about it! I trusted you! How could you do this to me?
You know, even though I can barely see past the pain of you two together, the hardest part about this is not even the fact that you’ve been sleeping with __(him/her)__ for as long as you have, but that you’ve been hiding it from me all this time, while lying straight to my face. What kind of friendship is that? Well here’s some breaking news for you, __(Friend’s Name)__. That is not friendship at all! Not even close! You have committed the ultimate betrayal.
Now every thought of you literally sickens me. It kills me to know the truth about you. Maybe one day you will see what you so callously threw away.
Your ex-friend,