Coping with dementia in a mean, selfish parent with guilt and anger. Any advice?

My biological mother, 78, has always been a mean person, except in front of strangers or other "worthy people" [read: people who go to her elitist evangelical church].

Out of 3 children, I rank #2 in her "affections", which are mecurial at best. Because God loves her so much [just ask her!] and he is sending me and my brothers to hell [no need to ask - she'll remind us often!], she claims that God is protecting her from Covid. She believes that all who've died were secret sinners, or just non-believers who don't matter in God's eyes.

The fact that my brothers (who dislike her as much as I do) are not flying in for Christmas is "foolish" on their parts, she says, and "cruel" to her as a mother. I am willing to drive to her house (30 very long minutes) to endure an hour or two in her presence, and that of my equally self-righteous stepdad is already not enough to please her, the Unpleasable One. There will be three other relatives there, two of whom repeatedly claim that they "don't care if they die". None of those people take any precautions at all. The fact that I do irritates my mother.

After being badgered in several whining, pleading, woe-is-me phone calls, I finally said, "OK, I'll come. But I won't take off the mask or the face shield; I won't eat with the family; and I'll only stay an hour." She fake-cried for a few seconds, and then got angry. Of course, my stepdad always takes "her side". He will certainly pull me aside while I'm there and remind me that they are immune to it, thanks to their God's protection, and that since I'm going to hell, it doesn't matter if I get it, plus "it probably won't kill you anyway."

I find them utterly intolerable. I'm having a hard time forcing myself to even call my mom and her husband weekly, which is a courtesy I've tried to continue since I moved out of their house for college when I was only sixteen and very, very angry at them.

But the truth is, I'm starting to (hate) them now. I mean, literally hate them. Like, want nothing to do with them, never want to see them again, certainly don't want to listen to the same six jokes I've been hearing for 20 years. I am willing to drive by slowly and throw their Christmas presents out the window and keep on driving!

But I will go.

I will be the "good daughter" through gritted teeth. My boyfriend, who is similar in some unhappy ways to my mother, says I should just stop communicating with them entirely. Therapists have advised the same, more than once. But I won't do it. I will continue to endure because some days, she will be the "nice mother" for an hour or two! Sometimes, even just for a few minutes, she will not whine, beg, threaten, cajole, implore and cry crocodile tears trying to force me/some other family member into doing whatever she wants done, or &itching about one of us behind another's back.

I feel bad about liking her less as she needs me more, and as her mind slips further away. She was hateful to the several elderly relatives she cared for back when she was around my age, and sometimes downright cruel. She always complained about them, claiming that "the mean ones live the longest." Now she's fulfilling her own prophesy and I'm sad/angry/confused/hearbroken that I'll never have a real mother.

Thanks for reading this "venting" email. I feel angry at myself for not liking her, and angry at her for being such a witch for the last 56 years of my 56-year-old life.

I'll go. I'll mask. I'll leave. I'll want to cry and punch her all at once, but I'll choke it down like I've always done. But as her dementia continues to unveil her sick mind and horrid personality, this gets harder and harder.