I was physically, emotionally and mentally abused by my 84 year old mother who now has Alzheimer's and dementia. Any advice?

If someone was biting me, no matter the reason, I would keep my distance, physically and emotionally.

She's been this way your whole life? I think anybody would excuse you from having any kind of a meaningful relationship with someone who abused you.

I don't buy in to that 'it's the disease' in all situations. Sometimes mean people are just mean.

I stopped seeing my MIL 3 years ago b/c she simply could not even bear the sight of me, literally. Sounds weird, but it does happen.

Cut yourself some slack and make your relationship with her as limited as possible.
Have you ever had counseling? Your post sounds like a scared 10 yo. Please think about getting some help.

Don t let others guilt you into seeing or taking care of this woman. She has always been evil and the dementia is magnifying that and you are continuing to be abused. Hopefully you are not living with her. I would cut ties with anyone trying to guilt you into seeing her and taking care of her. What a bunch of rotten people to want you to continue being abused.

No where is it written that a child is responsible for their aging parents care, ESPECIALLY when that child was abused in any way from that parent.
You owe her nothing, and for your own mental health's sake you need to step away from trying to care for her.
Like said, those that are trying to guilt you into caring for her, are those who themselves want nothing to do with her care I'm sure, so it's just easier for them to try and guilt you than for they themselves to step up and do it. That too is a form of abuse.
Quit allowing others to dictate what you should or shouldn't be doing. You know in your heart of hearts what is best for you, and you just need to do it.
Your mother will be just fine without you caring for her. And if no one else steps up to care for her, she can become a ward of the state, and they will oversee her care.

I was abused by both of my parents and I would never have put myself in a caregiver situation with either of them as it would not have been healthy for me, and I knew it. And I have absolutely no guilt over my decision.

Please take care of yourself first and foremost. and don't allow anyone to abuse you anymore in anyway!

You're being guilted into caring for this miserable old woman bc nobody else wants to, for obvious reasons. Either arrange to place her in Skilled Nursing or Memory Care Assisted Living, or to have caregivers come into her home to look after her. On HER dime, of course. If you're living with her, move out after arranging for her care. Physical abuse on top of emotional abuse is 100% unacceptable. Anyone telling you otherwise is gaslighting you.....trying to make YOU feel crazy for wanting an abuse free lifestyle. Just bc she has AD is not a free pass to bite you, curse at you and fly into rages. The woman needs calming meds STAT in addition to the rest of it. Behavior this unhinged needs medical intervention. Next time she's flipping out, call 911 and have her taken to the ER for a psych evaluation. Then refuse to accept her back home. The hospital will have to find residential long term care placement for her.

Detach yourself from this nightmare immediately.

As someone else mentioned, leave her to the authorities. You were not placed on this earth to be used and abused by anyone. Verbal abuse and physical abuse are non negotiables. Someone that out of control needs medical intervention as in a memory care unit or a long term facility. Placement is key here. Push come to shove, have her admitted through an emergency room. Tell them you cannot take care of her because you do not have the financial resources to do so. If she has no resources, Medicaid will kick in for her care. I would have as little as possible to do with any of this other than dialing for an ambulance. This would include no signing of the POA or anything else that will keep you connected.

Since your mom has been abusive to you since you were a child, the dementia removes the filter making her even more abusive.

You do not need to become a hostage and slave to a miserable, mean and abusive old person. Don't allow people to talk you into taking care of someone like this. It doesn't get better. You won't like her or yourself for allowing her to treat you badly.

"It's just a disease", they tell you?
How does that explain the fact she abused you for her entire life?
Please seek psychological counseling for yourself so you can finally seperate yourself from this woman, who, I believe you are indicating, was abusive all of her life. Allow the authorities of the state to handle her needs as she fails and make a life for yourself that does not involve abuse.
I wish you the best.