I don't think her being a normal character would work with the lore, since she should be stronger than everyone else already, and she would overlap with Elsword.
My first guess was that she would be a sheath knight NPC. But that seems like too heavy marketing for an NPC, so it should be something bigger...
Maybe a special playable character, but I'm not sure how special. Hopefully not CASH-only crap, that would be dickish and make even more people quit.
If she is playable, I'll most likely try her out since Elsword is the only playstyle I really enjoy. Though I haven't tried Ara, maybe after she has 3 classes.