Welcome to SR, crazed. I am sorry for the situation that brings you to this forum, but glad you found a place to bounce stuff off of other people who have been down this road.
I would put my money on you are both crazy at this point. I know I was...being in a relationship with an active addict makes you totally nuts. Its a crazy train ride and a total mind-trip. And it is this way because it protects the users addiction and behavior while using. They can't function any other way. I mean, look at the damage left in the wake of your GF...do you really think she has the capacity to step up and face all that? Sheesh- I feel a tiny bit guilty for her just reading this.
Ok, so your crazy - well luckily for you, that's fixable. Maybe instead of focusing so much on her, and trying to salvage this relationship right now, how about dedicating your time and energy on yourself, so you aren't crazy anymore? Imagine a peaceful, predictable life full of joy and serenity. Is that what you want? Then go get it. If not, then stuck with your drama - much of which is self-perpetuated.
This is where you have choices and control. You can't control her - that much has been proven over and over again. But you can control how you want to live your life from this day forward. You can protect yourself by setting boundaries and following through. I know one of my hard fast boundaries is no affairs. That's a deal-breaker, period. What are your relationship boundaries? If you can't answer that - a good therapist can help you work through your stuff until you find your comfort zone with boundaries.
Al-Anon is a great resource that costs a buck or two per meeting - but at this point, if I were you, I'd go full on recovery mode and hit it on all fronts: Al-Anon (sponsor + step work), self reading, personal therapy, etc. Because being crazy is no way to live - you've got this one shot at this one life. Why waste it living it in such a state of un-manageability? I think I just made up that word! ; )
Keep reading here, and keep coming back. After several years of crazy, I am completely and totally grateful for mustering the courage to step off that crazy train ride and find serenity and peace in my life again. Hoping for the same for you.
~T