if you know for sure that she is straight and has absolutely no feelings for you "in that way" you shouldn't tell her...she might think your wierd and tell the whole world! Plus your young and your feeling might be all mixed up right now...in a couple of years these feelings might go away or might not...
you said you've already been through too much... sometimes when ur young and still finding ur sexuality u end up reaching out to people in ways u wudnt if u met them a few years latter.
i got with my girlfriend after a serious attack and its taken 3 years to establish our relationship. Its been a constant struggle to prove our feelings for each other are genuine.
Often in gay relationships one of the main reasons that u identify with that person is that you both feel alienated and find it easier to relate to someone of same sex. Sometimes you're not sure enough in yourself to be able to think sexually about people you wouldn't trust as a friend.
These are reasons why you might end up feeling like u wanna be with ur best friend but if the attraction is coming from an underlying fear of men you could end up repressed in the same way as someone who is gay and trying to live in a straight relationship.
You right, until u are completly sure ur attracted to some one for the right resoans and you feel theres a chance they might feel the same there's no need to broadcast ur sexuality. Be sure of your self; dealing with others prejudice come later.