Well your like me in the sense, you'll never actually put the thoughts into actions.
I've been in the position you've been in, but with a girl ALOT further away from me, and not knowing, etc. Never found out, and never will probably.
Don't miss a chance is all I can say
I know your worried about losing her if you tell her, but what your feeling is a natural thing towards her. You can say it in such a way that if she says no, you'll most likely carry on as normal. If she says yes, you have a chance!
(Heck, I should use my own advice like I've been saying, but yeah, I know how hard it is mate)
not gonna lie. you kinda let me down, lol. BUT! it sounds as though she perhaps feels about you..the same way...perhaps not as obessive but summon up the courage and find out for yourself.