'Emo' is short for 'attention whore.' Emo chicks are retards who never properly hit puberty, and are thus left floundering, trying to impress emo boys with their greasy hair and black nailpolish.
Bisexuality is also a popular option for emo girls in middle school.
"I've passed by that emo chick a couple times in the hallway. I hope she cuts herself to sleep."