I have a 2 faced co-worker who's not happy about my promotion and is trying to get me into trouble with my General Manager . She's making up stories about me and she's getting very bitter about it . She's friendly to a point , but her true color's are showing . She's very mad about her hours being cut and has threaten to leave to some of the managers . She view's me as a rival (I haven't done a thing to bring this on) and she admitted that she has "manic depression" which makes her very emotional on the job . Because I worked for are General Manager before working at are current job , she thinks there's a unfair favoritism , but the thing is he's very aware of my abilities and that's why he promoted me .
So my question is what should I do ?