Well its the first case i heard a girl was 'THAT' persistent, 12 years long is just wow, in not giving up into willing to wait for what you want. From your point of view it must be the worst thing, but you have no idea what has happened behind your back. It basically meant that you have been her rival for a 'long' time, and that she has been planning 'all sorts' of things into getting him into her world.
I don't think you expected her to deliver 'that' kind of a fight into conquering him. But to be honest i don't think their relationship will last that long, i mean if 'he' really saw something in her then he would have dated her 12 years ago, i say give it 6-8 months and they will have splitted up again, you just have to be like a fishermen and have patience till the fish come biting again.
If i where you i suggest you don't aggrevate yourself over this, I think that if you give it time , he'll come back to you but not immediately, it will take time to realise him the exact reason again why he didn't date her for all those years to begin with.
