Let me get this straight your ex gf cheated on you with your best friend WHILE YOU WERE IN AFGHANISTAN for over a year! then dated him for almost a year although he should have known if she were to sleep with her boyfriends bestfriend she would then end up cheating on him too. Which of course she then cheated on him too AND then he is mad about it and is kinda rude to her (which she deserves) and you of all people are going to get involved and back HER UP. 

You gave me HELL for even thinking about FORGIVING my ex for cheating and here your ex NOT ONLY fucked your bestfriend while you were gone but she dated him. if i were to back up my ex you would stop talking to me why is it okay for you to but if i did all hell would break loose? How can you honestly want her back or want to have anything to do with her after everything she put you through. you deserve so much better. I know you say your not but you’re a GREAT guy and you deserve the best and to be happy and shes not gonna change once a cheater always a cheater. 



Whatever bro good luck.