Lord have mercy!
I just wanted to offer some words of encouragement.
I was agnostic atheist from 2003 to 2010. 7 long years. This year (at my first divine liturgy, April 25th 2010), I finally found my home in the Orthodox church. It may take awhile. Have you taken her to your church yet? My problem was this: I had no idea that there was something besides Catholic and Protestant. I left Catholicism and did not feel at home in Protestantism either. I sort of "defaulted" to agnosticism. Also, it can be very difficult to have faith. Perhaps she didn't know that Orthodox Christianity existed before and never got to look into it?
However, something in my heart told me that there was something called Orthodox Christianity and to search for it. I found a church in my area and I felt called to it. At my first divine liturgy I was changed, now a happy Christian (while I am not Chrismated, I was baptized Catholic so now I am officially "Catholic-by-default" though my heart is in Orthodoxy).
There is still hope for your girlfriend