Should i tell her how i feel or keep things how they are?

Ok so there's this girl I've been friends with since 6th grade. We call each other bro and sis. We talk alot and have many laughs together and have alot in common and have always been there for one another. At first in 6th grade after a while I tried telling her how I feel but she had a boyfriend so I couldn't. So I've tried suppressing my feelings for her and it worked for a few years and now were going to the 12th grade. Over time my feelings have come back and I like her alot but don't know if I should try and get her or just keep things the way they are because I don't want things to be awkward. So what should I do? Tell her how I feel or keep things how they are?