Tips for dealing with mentally abusive parent?

Is she still living at home and is she living alone? If so can she manage on her own?
If she can not manage on her own if she refuses to move to AL (or Memory Care if she has dementia..((and if she does she should not be living alone)) You can hire someone rather she can hire someone to come in and take care of the things that you have done. Fix some meals, clean, do laundry. If she has not been diagnosed with dementia and can understand and retain conversation tell her that you are going to step aside because of her treatment of you.
Discontinue any financial assistance. She should be able to manage with her income. If not time to cut back on spending and apply for programs that will help with utilities, food and other needs.
There is no need to take abuse from anyone that is cognizant. (and limited verbal abuse from one that is not) Physical abuse...NEVER from anyone!!! (anytime)

My mom has a diagnosed personality disorder. She is a bottomless pit of rage, abuse, neediness.

I would consider walking away from her for a set period of a month to get some piece of mind. These people can be like battery acid poured on your soul.

You can make a rational decision after your break to leave for good or to set strong boundaries. Both are equally great choices.

I don't know about 'walking away' entirely if you are the only one of her children who lives locally. I do know that you need to set down some rules and boundaries for what you will and will not do for your mother, based on what YOU want. First off, I'd cut her off financially 100%; she needs to live within her means and you need to keep your own hard-earned money for your own needs and for your own future retirement. Your mother has no right to 'demand' anything from you..........she can either ask nicely or fuggedaboutit. You can pick and choose which 'favors' you'd like to grant her, and which ones are above and beyond what you care to do. Some people, like my 93 y/o mother, is never satisfied no matter HOW much she's given, so what's the point in even trying? You have to realize that and make your future decisions accordingly. Jumping through fiery hoops to no avail makes no sense. Stop doing it. I did, long ago, when I realized I was getting burned each time, and now I feel happier as a result.

Decide when you will visit and call, how much time and energy you will devote to her, and then move on with your life. She won't be happy ANYWAY, so what's the difference? Once you grasp that idea within your mind, it's easier to stick to the new boundaries you create.

Good luck!