In 2 minds, please help..

Hello all, I'm currently in 2 minds and I have no idea what to do. I'm talking to this girl and I really do like her, and she is openly Bisexual. All my friends have heard about her, but only know we are friends. I am a quite girl, but known by everyone. I do want to come out and tell everyone that I am bisexual and tell everyone how much love I have for this girl but, I am so scared as I know how many people I will be judged by. I know that my family will be supportive, but I also know that my father and brother will be awfully childish about it. Let alone all the children in school. Do i keep on talking to the girl and get into a relationship with her on the down low, or do I just tell people? And if you believe that I should tell people, what is the easiest and least embarrassing way to do it? Thanks for taking your time to read, and please comment any suggestions xx