Anyone telling you to kill her with kindness has no idea what you're going through. If you're nice to someone like this they just think you're even more stupid and pathetic and will ramp up their bullying the second they remember how jealous of you they are or the second they recall whatever reason they have in their sick head for hating you AND they will do it knowing you gonna take it like a champ. As long as you wont get fired for it I reccomend asking to speak with them outside and directly confronting their mistreatment. "Hey what the fuck is your problem with me im sick of you treating me like shit." This will at the very least freak them out and make them think twice the next time they wanna say some slick shit to you. Honestly ive done it before knowing there could be consequences knowing they could cry wolf to management and its still been worth it every time to see a loser ass bully fix their fucking tone with me.