hahaha dude!
sorry, i had to laugh...but only because i feel your pain.
i went through a similar experience. VERY. SIMILAR.
here is what you do:
1. first, you concoct a story (in your own mind) of some huge life-altering event!
(for instance: going overseas on missionary work, recently discovered you are gay, you've been diagnosed with terminal cancer, you've recently converted to a new religion and have no time for relationships, etc) you get the point!!!
2. second, you call her! and you sell that motherfucking story. you sell it like your life depends on it. GET DRAMATIC if she protests! turn it around on her about how hurt you are that she can't understand how difficult this "sudden life change" has been for you.
3. third, finish with "well i am sorry that we can't even be friends, but i'm moving on with my life now. goodbye!"
4. fourth and finally, you cut all ties. ALL TIES! you hear me?!!! if you fuck this step up, your life is doomed! she will forever haunt you.
PS - before doing any of this, have an escape plan, change your phone numbers, phase out your email accounts, or at least switch all your other contact to other emails, so that you can shut that one down on a moment's notice, fucking disappear off facebook. dude, you need to go into stealth mode!
good luck, man. you are going to need it.