At 89, how's mom getting around? How's her health and competence? Are you in the home as a caregiver? Do you provide her with any of her care? I can understand that it may not be at all feasible for you to move out at this point. So it sounds as though the three or four of you are involved with ownership of a house that belonged to a daddy who died intestate, splitting up his possessions in this manner. So she's not completely the deed holder to the house, huh?
If this person has been verbally abusive to you all this time, and she knows you don't have any way to leave, or any place to go, no matter what she says or does to you, it's like giving her complete power to have any kind of tantrum she wants or can think of to have, knowing you won't leave, can't leave. Now she's hit upon the idea of threatening you with calling the police and saying "elder abuse!"
It comes to me that if you did suddenly win the Powerball and move out, she'd be sort of up a creek, having lost the housemate who may be making it possible for her to live there independently. Also, you'd have the ability to just get up and walk out of a visit if she began talking ugly to you. It's amazing how much that would probably cause her to change her tune, if she is still is in control of her mental faculties at all.
My mother used to threaten to call the police on me and throw me out of the home I lived in (which she owned) but it was mostly just bluff. She would also rub eye make up on herself and let people think she had suspicious bruises, hinting broadly that some family member (probably me) was beating her. Sad but true, mean people get old too, and they usually don't then change the attack patterns of a lifetime.
My defense was that those around me could see that through all this wild talk, I was taking good care of her, doing her lawn, doing her home maintenance, getting her groceries and taking her to her medical appointments, washing her clothes. If you are living there with her rent free, I'd make sure I was doing all those things, not just acting like a star boarder while others do those things you could be doing to pay for your residence.
OP, I'd suggest that instead of worrying that you'll be charged with elder abuse, make sure your behavior is exemplary, DO NOT fight or argue with her. Talk to someone, get some guidance and good counseling if possible to help you try to break the patterns of a lifetime, even if she cannot. If you or she has a church home, speak to your pastor or spiritual leader, or seek some free counseling from a clinic. But this is not an unusual situation, sadly. And I can see it not from the mother's point of view which of course tells you that you are a deadbeat who can't afford to live anywhere else, instead of a child who is staying there helping her in some ways.
