How do you deal with mean girls in the workplace?

How do you deal with mean girls in the workplace? There is this girl I work with who used to be my friend. I stopped considering her a friend when she invited me to a girl's night out and then ditched me in the apartment while I was in the restroom. But we still work together. She constantly rolls her eyes, sighs or mutters under her breath whenever I speak. One day, I heard something loud in her direction so I turned towards her and she was staring at me with the microexpression of anger. When I looked at her, she just rolled her eyes, looked down and ignored me. She has also tried to complain about me to our mutual friend who is our Shift Lead right in front of my face. I looked at her and she just smirked. When two of our coworkers started speaking to me and joking with me, she started shushing our conversation and saying we were talking too much then proceeded to speak to them for 20 minutes before going on her break. Whenever I say anything, she seems to get upset or irritated with me solely for existing. But she has also been there longer and is friends with everyone. Our other coworkers also don't seem to notice her behavior towards me and if I took it to our bosses, they would probably not believe me. So how can I deal with a coworker who is a mean girl without becoming a mean girl myself?

How do you deal with mean girls in the workplace?
Post Opinion