This sounds just like a witch I was forced to work with for 2 and half years.I left my old job because I had a colleague who was just a literal nightmare. She was always careful to save her outbursts for days when management were working at other sites. She'd complain about her workload (even though I actually did a few tasks that were within her remit because it was easier for me to do it than to have the battle with her). She would yell and scream about all sorts of things, have complete meltdowns about her boyfriend having to go away for work. It was constant. She was always bitching about other colleagues while pretending to be nice as pie to them. I was really friendly with her initially but I just couldn't ignore her behaviours anymore ( I also found other colleagues difficult to gel with, they were a bit cliquey but nice enough). I'd try to pacify her when she was having meltdowns, tell her to go and take a 5 minute walk to calm down, she never did. She wanted the attention.
She'd constantly be emailing managers asking for a payrise, and not understanding that she was underperforming. I earned a little bit more than her, but only because my role was a bit more specialised and technical (she was first line support in an area, I was second line support in a slightly different area if that makes sense). I didn't realise how much she actually resented the fact that my role paid more.
She then started saying stuff that made me so uncomfortable. We had a colleague who bless her heart was lovely, but just really not great at the job, so would ask questions a lot. It required a lot of patience. My other colleague would be nice to her face and then one day she turned to me and said I can't fucking wait until she leaves, fucking bitch. There were other instances like this. We were having a move around and the person taking my job was going to have my desk, and she said she better fucking not sit next to me that cow. Then turn around and ask her how her wedding planning was going and how excited she was.
Anyway, enough was enough and I actually ended up signed off work for a couple of weeks because it was another thing stressing me out on top of other things going on. I came back and wanted to leave so had applied for other jobs. While I was off she'd gone around telling everyone in the office what a complete bitch I was for not telling her that I was going on sick leave (yes, really). Things all started coming out and it was clear she was playing colleagues off each other. She'd talk about another team to me, but then she was talking shit about me to them. She said I was overpaid and a stuck up bitch. She had said awful things about my colleagues such as because they were privately educated, they didn't know how to socialise in a real job etc. We ended up making a complaint to management about it (she was underperforming, so an investigation was already ongoing). She had a meeting with management the week after I left and apparently she went absolutely ballistic and said I'd conspired to get her the sack or something.
I hope to christ I never see her again, she is just horrible and I'm still a bit sensitive about it all, this was almost 2 years ago. Thankfully in my current job, everyone is pretty relaxed and I work in an office on my own!
She made everyones life a misery.