Dear …
I am writing this letter to tell you how appalled I am at the recent behavior of my ex-(husband/boyfriend/girlfriend/wife/etc.)__and how unhappy I am because of what it has done to us. I see now that __(he/she)__ will go to any lengths to sabotage my happiness with you. When you told me of the things __(Ex’s Name)__ said to you, I was both shocked and very angry about it. I can understand why this would upset you, __(Name)__, because if what __(he/she/)__ said were true, it would be enough to upset anyone. The difference here, however, is that there is absolutely no validity or truth, whatsoever, to any of those things __(he/she)__ told you.
I can’t imagine what __(Ex’s Name)__ was thinking when __(he/she)__ did that! Is __(his/her)__ mind so warped that __(he/she)__ somehow thinks by interfering with and destroying my new relationship, that I will actually go back to __(him/her)__? I can now see that it was a grave mistake to try to remain friends with __(him/her)__ after we broke up. It is clearly evident that __(he/she)__ cannot bear to see me happily flourishing in a romantic relationship with someone else.
My best guess is that, while __(Ex’s Name)__ was camouflaging __(himself/herself)__ as my friend, __(he/she)__ got your phone number from __(describe where the ph # was retrieved from)__ with the full intent to cause destruction between you and I. I am extremely disgusted by this whole thing and, obviously, will never allow my Ex anywhere near me from this day forward.
Now I am asking you, __(Name)__ to see this for what it really was—simply a blatant attempt to come between us, based purely on lies. I’m asking you to ignore everything __(he/she)__ said to you because there is no truth to it all. You mean __(so much/the world/etc.)__ to me and I always look forward to every moment we spend together. My heart is truly with you and no one else. I am missing you so much, __(Name)__, and hope that you will be able to get past this. I hope that you believe what we have together is worth __(fighting for/giving it a fair chance/etc.)__.
Yours,