I finally unfriended the old/new girl from Facebook.  It is a sad day for me.  I think that's part of my problem, I didn't want to mourn the loss of someone who I felt so strongly for.  She's not dead, but lost from my life, forever even.  That is such a strange thought to me.  And it's so crazy to me how all these feelings got ramped up and I never even saw her in person.  
Yah, when I went through something similar (reconnecting to old b/f without ever actually seeing him again) I told my T it felt like drug withdrawal. She said physiologically, it is the same thing. 
I'm beginning to think a huge part of my dysfunction has been living in fantasy worlds I build in my head. Either that, or constantly seeking them out in real life. If it was a bad fantasy, I would feel anxiety. If it was a good fantasy, I would feel an almost compulsive attraction, or even adrenaline, which made me ignore the danger or pain. 
When I stopped letting myself build fantasies, I had to wade through a whole bunch of painful feelings. I'm not done sorting my way through all of them, but enough to realize now that a lot of what I was doing before wasn't real. 
You know how people here always say that other people are boring? I finally realized that it's me who is boring     Kinda hurt going through that process... .actually, it hurt like h@ll. But now it seems almost funny. I don't know why I was so afraid to feel my feelings. Being boring and lonely isn't nearly as awful as I thought it was going to be.