Cat Fight

So I've mentioned in a few previous posts that I currently work at Jimmy Johns. Its not what I would have wanted for myself at this point in my life, not the glamorous job I dreamed about, but whatever. . . Well this girl, we'll call her Catface, who just got demoted from a management position, and they promoted me to her position. Unfortunately, since Catface was only demoted and not fired, I have to work with her during many of my shifts. This makes me feel uncomfortable because 1. I am new to the position and don't know everything yet 2. Catface is fine one minute and then incredibly snappy or rude the next and 3. I instantly get in a bad mood every time I see her, whether or not I've even talked to her, right as soon as I see her I get on edge and feel like slapping her. This is so immature and childish - I'll be the first to admit it, but I still don't LIKE IT! I didn't like her before I got