It's a new word the **** are using to describe the sad, depressed ****.
You'll be able to spot an emo when you see them, because they'll have jet black hair with purple highlights or whatever (others will go blonde, with purple highlights or whatever). More often than not their hairtyle will be wierd so that it covers the eyes, and they'll always act all depressed n stuff.
It's basically a fasion/lifestyle accomodated by "emo" music, which is a part of hardcore punk music.
So no she's not an EMO, but she's somewhat close =P
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