Sister is becoming friends with the brother of the girl who made me try to kill myself?

I agree with railroad dave's comment. You are responsible for your own happiness. No one put a gun against your head and asked you to attempt suicide. As much as i would love to point the finger at those who have done wrong by me and blame them for my dissapointments, i remind myself that my value and self-worth does not reflect what these ppl have said and done. Its not about her. Its personal issues and humiliation that u need to be brave enough to accept and face. As for your sister, you cant pick and choose her friends. The girl's brother and your sister have nothing to do with your past feelings with this girl.