Hi Tavs
"Her coping mechanism while making this tough decision is to totally shut me out." By Tavs
Coming back to my earlier suggestion. Her coping mechanism is to shut you out at this stage so there is nothing you can do or say to change that. You need to give her time and lots of space without YOU in the pciture (I think 2 months is going to be enough). That time will either make her or break her. Fixed lease agreemnts can be broken if she feels strongly about her mistake (It happened in the past).
"She'd never make any promises to me right now" By Tavs
I think it's very crucial to both you and her that she makes this promise. I mean, what have you been waiting for these past 4 months??? Tell it to her this way, this promise is the keeper of your relationship. If she makes no promise of being faithful to you then it is all over and make sure she understands that right there and then. Her not being faithful to you means you walk out from that conversation with her today and from this day onwards you move on and completely forget about her. Because its really going to kill you being in a relationship like this. If she DOES make that promise then give her time and revisit this in 2 months (You will still need to move on just to be able to pursue your life from this stage). It's hard i know, and it's very hard to give advices like this, but the way i see it these are you real options. You said it yourself there is not chance of you moving with her.
Hope above helps and best of luck!!!
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~