I'm really sorry that things worked out this way- it's sad to see a long friendship like that end. But how petty of her to behave the way that she did- you expressed your concern for her, and she thanked you by demoting you, then hiding her true feelings from you for so long. Bah!
Keep your chin up, and I agree with keeping a journal about this, if you're into writing. It may help you process this whole thing.
