When was the last time she ever said anything about you moving to where she is.
Sounds to me like she was just not into you & the move gave her a chance to live her life the way she wants. If no commitment was made to stay faithful to each other when she left then she in theory is not cheating on you.....
Why in the world would you even want to stay with someone like her in the first place?
I was still married to my H when I left him (bad marriage)....being away convinced me that I never wanted to go back or have him come to my new home. Sometimes being away clarifies things for one person even though it leaves the other one up in the air until the state of the relationship is finally cleared up.