Sometimes this can be a good thing, especially if you end up with a lifelong, mutual friendship. I know it probably hurts now...may be that way for a while, but life still needs to be lived, you know what I mean?
Stay in touch- you love her, you still care, why not stay in her life, at least for now, as her friend. Everyone needs those, life's a lot harder without them. Who knows, she may wake up tomorrow and realize the mistake she's made- whatever you do, don't hold it against her. Everyone's different, we don't all approach situations exactly the same so be understanding, be available...just be her friend. It seems that is what she wants at this juncture.