I don't know the best place to post so I've opted for AIBU for traffic. I've NC'd as this could be quite outing.
As background I have mental health problems and have done for years I'm high functioning and manage a day to day busy job despite crippling anxiety some days. Negative intrusive thoughts, all sorts. I'm regularly seeing my GP for help and waiting for counselling.
I work in a small company (about 15 employees). The boss is high maintenance but generally a good person I've learned to read him well and I manage his moods to mostly help myself.
The boss' mother also works in the company. They have a very poor mother/son relationship and rarely speak. They've had problems since boss was a teenager and have gone through various periods of NC. He desperately needed help in the business a few years ago (before I started) and she offered to help him out. She is paid a very good salary for her role so understandably doesn't want to give it up. She is very vocal about how much she 'hates' her son! Yes she's actually said that. She says the most vile things about him, one that particularly stuck in my mind is that she wished she'd drowned him at birth. Truly hideous and the most difficult thing to listen to.
I've spoken to my boss about her behaviour but for obvious reasons I haven't told him exactly what she's said. She mostly works remotely but comes into my office once or twice a week when I have this sort of conversation from her. For the last two weeks I've avoided her saying I need to be in external meetings. I can't keep doing this.
It's actually destroying me - the boss has said he'll sack her if I want him to but I don't want to be responsible for that.
How on earth do I deal with this almost impossible situation. I've told her I don't want to listen to it but she's a very argumentative and confrontational woman and I can't bear to get into that sort of situation with her.