Wow, that's rough. At this point there is only 1 (actually 3) things you can do, bang her sister/best friend/mom.
All jokes aside, I'm really sorry to hear. How old are you? Did she give you any reason for it at all?
I hate to say it but almost all women are so insecure/evil that they wouldn't ever break off a relationship without having someone else lined up...
Like monkies; don't swing from the branch without another in reach.
Wonder how many hours he works.