Does anybody know how to turn a REALLY bad singer into a REALLY great one?

I'm a 14 year old girl. My voice is kind of annoying. I really really love to sing, but the fact that I'm a horrible singer stops me from singing in front of others. I guess I could call it tone deaf. I love being in musicals & stuff like that, but I can no longer do that because I'm not a little kid anymore and I'm embarrassed to sing. I would really appreciate if somebody could tell me if there's any possible way to fix my problem and if so, how?