Had I been in her position, I'm fairly sure I wouldn't have written at all. If I had written, I think I would have said something more along the lines of, "Everything is so much clearer to me now that I know you have a girlfriend." And then I think I would have let it go. The communication with him, that is. This is not at all to say that I wouldn't be hurt, but that I think my response would be to display dismissiveness toward him and deal with my hurt by myself. My friend had a counter-argument, of sorts, to this behavior. She said that the first time she had been in a similar situation, she had put on a show of not caring and being happy for the guy and that, afterwards, she had always regretted not letting him know how she really felt. In the future, she didn't want to pretend she wasn't hurt by the behavior of others.
I have been the recipient of my fair share of post-break-up letters and the like. They're always painful to read, but I save them and, occasionally, I go back to them. Usually, it seems, at the end of other failed relationships, to torture myself further. But they also kind of cheer me up in some, no doubt sick, way. I have a note that was slipped into a book I was reading at the time of a break-up that simply says, "I love you. A." that I've carried in my wallet among my various membership and loyalty cards since the day I discovered it. When I come across it by accident, it makes me happy in that stabbed-in-the-heart sort of way.
But I've never sent a post-break-up letter myself.* I have written such letters, but never given them to the former lover. I guess I have a fear of vulnerability. Also, I think I have behaved thinking that one's mourning is one's own and not something one should (or perhaps even can) impose on another person. While they are ostensibly a way of communicating one's feelings, break-up letters often also serve (intentionally or otherwise, but usually with some intention I think) to cause guilt or remorse in the other person. The writer knows that that the contents will hurt the recipient, and the letters may be written as a way to share the pain of a break-up rather than feel that one is experiencing it alone. But, while we are all in pain, we also all break up alone. Each person's pain is his or her own, and though it may be some consolation to know that the other person is also in pain, I don't think it actually reduces the pain or speeds the recovery. In fact, knowing that the other person is suffering may prolong it. (Or so suggests some theory I am developing in my head right now.)
*I have sent exactly 2 apology notes. One quite brief one rather long.
However, given the relationship I have with the break-up letters I've received, I wonder if my thinking is (at least partly) wrong on the subject of whether one should or should not write one. (I am working on another theory in my head right now which suggests that perhaps one should write what one feels at the time of the break-up, but share it much later, after reflection, but I think there's a fair chance that this is an absolutely terrible idea.)
My friend probably texted this guy back last night when she got home. She had more she wanted to say. I doubt she will actually sit down and write him a lengthy response - I don't think their relationship was so significant that it would inspire that. But I'm left wondering whether her response (i.e., tell the person what you're feeling, that what they've done has hurt you) is productive or counter-productive (or, you know, without effect).
So, post-break-up communiqués: Yea or Nay?