A few months ago i was at the point of completely giving up. My girlfriend, almost lifelong friend, took a walk with my best friend. It caught me so off guard, I never saw it coming! And I just wanted to die.
I'm so sorry for what your girlfriend did to you. In the physical realm, we don't understand it and we think we don't deserve this. However in the spiritual realm, God is at work in you for the better although we don't see it now but we will in the future. We have to just rest in His love, trust in Him and seek comfort from him
Conversely, God set us far apart which has helped, but now I am heading home and I am not looking forward to the reception. My church loves her, obviously I did something to drive her into sin. Most of my friends and "family" actually think the same. I may have to move in order to just have in person friends again!
But, I learned that all is not well for her, God seems to be making her life tough - I am assuming to call her back to Him. This is to the point that she is now where I was months ago. I do not want her dead, I know that I have to forgive her, but forgetting the betrayal will be a little harder. But, then I maybe be getting a head of myself - she still has some apologizing to do first.