To be completely frank, I can empathise totally, having had a similar situation myself a long time ago (afc days for the win! lol). Where there may have been a spark initially, your 'chances' are gone.
Your only choice is whether your want to be friends or you want to get it off your chest, and essentially, kinda lose what you had. Its that simple.
You have oneitis; my only advice is the show the white flag, and give up on this girl, as hard as it is. There are a couple of billion girls on the planet.
READ this forum, and learn some pick-up techniques on approaching, opening etc. Then make posts, asking for help, and then practice your game.
Being AFC, you probably think this'll make you 'evil' or 'a slimeball' or whatever, but it couldn't be further from the truth. Even if you eventually take the foot off the pedal actually picking up girls for fun - this stuff will actually increase your confidence socially. This means? Meeting new friends, and more importantly, giving you the courage to talk to and immediately convey interest to a girl you like.
There will be no more pining, no lack of balls that puts you in the friendship zone rather than relationship material (cause of your pining i believe), and I can guarantee a better quality of life.
Either go and talk to that girl normally, accept your are friends and MOVE ON or tell her how you feel and MOVE ON that way. Either way this ones a dead end.
Look forward to seeing your posts as you join the dark side

lol
Good luck.