One way or another you are going to have to come to terms with this and move on. Only then will you understand how much better off you will be.
After she gets done fucking this dude she will more than likly come running back to you. When this happens you should do the following. (Worked very well for me when I got cheated on by someone I thought was the love of my life.)
First be really nice. Keep things smooth for a while. Then start juicing and taking total care of your bod. Buy yourself some new threads and get a tan. Then start trying to fuck each one of her closest friends one by one. This can easly be done, you just have to know how to put yourself in that position. Take pictures of each one. This could take upwards of around a year or so...so be patient. You have to be mentaly preparing yourself the entire time to be single. Then after you have fucked her closest friends give her the pics and say a big fuck you. The idea here is to use her as an emotional crutch while you are slowly working your way out of a slump.
After she gets done fucking this dude she will more than likly come running back to you. When this happens you should do the following. (Worked very well for me when I got cheated on by someone I thought was the love of my life.)
First be really nice. Keep things smooth for a while. Then start juicing and taking total care of your bod. Buy yourself some new threads and get a tan. Then start trying to fuck each one of her closest friends one by one. This can easly be done, you just have to know how to put yourself in that position. Take pictures of each one. This could take upwards of around a year or so...so be patient. You have to be mentaly preparing yourself the entire time to be single. Then after you have fucked her closest friends give her the pics and say a big fuck you. The idea here is to use her as an emotional crutch while you are slowly working your way out of a slump.