I'm sorry that happened to you, it's wretched.
Are you able to step back and not go round so often? Or stop altogether for a few days? Then, when she contacts you again you can say "You called me a mean bitch on Thursday, mother, and I will not tolerate that language from anyone." There are solutions which might make things easier - online shopping, social befriender visits, etc.
You could also make a plan that, when you're there, as soon as any nastiness starts, you simply stop whatever you're doing and leave. Just go, without comment or reaction, or nothing more than "we've discussed this before, mum. I'm not going to be spoken to like that. Goodbye." If she doesn't get a rise out of you, it's less fun for her.
Another option if she persists and basic tactics don't work might be to say "Mother, if you cannot be civil to people trying to support you, then perhaps it's time to start thinking about residential care."
I know it's not easy being elderly, but it's not a free pass to be abusive. And you don't have to take it, any of it. You can't set yourself on fire to keep another person warm. You are important too.
If you haven't already found it, there's a long-running thread on MN called The Cockroach Cafe - it's for people with challenging elderly relatives. It's an absolute haven of kindness, wisdom and support of the very best kind. There's a virtual comfy bench for the vastly overpopulated "bad daughters' room" with gin and biscuits 😏- here's a link: Cockroach cafe Summer 2025 | Mumsnet
Very best wishes to you. I hope things get better for you. Posting about this doesn't make you a bad person. You sound like a lovely, caring person who has had enough, and you do get to call time on this if you want/need to. Adult Social Care can step in if you need to remove yourself. x