Do nice girls always finish last?

Basiclly my group of friends excluded me out because I defend the people they mock, befriend the friendless, & just an overall nice person. Now I sit alone at lunch (because it got around that if anyone sat/talked with me...they'd spread a bunch of rumors about that person) Ive been friends w/ these girls since kindegarten & they dumped me in a second!! I dont want to be alone all the time, but everones too scared to be friends with me! What can I do?