Why is she so popular? She is ugly and mean!?

She wears loads of make-up, sticks her out, snogs loads of guys, she is mean to me but everyone thinks she's nice. People say I'm pretty but why do they always make fun of me? They spread rumors but why? I'm not a threat to her, I not stupid enough to not care who I'm snoging and stuff. Why do they all love her but detest me? What should I do? I've tried everything!