Im a Lesbian, but Im afraid to tell my parents? Help.?

I know my parents will accept me, but I know they'll bug me about it, and I have 2 sisters and another brother, they all except gays, but My one sister doesnt. She always makes these remarks on how its bad to be gay, and we get into a lot of arguments. Not, only is she hurting me but she's hurting me because I have friends who get made fun of being gay all the time. Im only 15 and my other sister who doesnt like them is 17. I never told her that Im a lesbian because I think Im more of bisexual then anything. But, still. How do I go about this?