I am angry with my sister but my parents dont care. Help!?

I am 14 years old in the 8th grade as is my sister Melissa. I am really pissed off because I am getting harred and bullied in school by my guy friends and other guys. My sis Melissa is a cheerleader at our middle school and a lot of the boys like her. What ticks me off she wears thongs to school under her skirt and jeans also. Sometimes the boys can see them when she leans over with her jeans etc. I always get comments that " your sister has a hot " or " your sister looks hot in that thong ". Its so embarring and Melissa doesnt care. The other day I had it though as this one guy told me " When I see your sister in that thong, I go home and jack it off to her ". I am getting tired of it. I didnt tell my mom about this but am I a snitch if I do? Melissa doesnt seem to care.