My mother is and was mentally abusive to me and my belated father. It’s very hard to be in touch with her on a daily basis. Advice?

I don't include mentally abusive people in my life. I would advise you stay out of contact with your Mother. She should be informed, if she expects help, that she should go into LTC that can assist her with her daily life. Do remember that there are many out here without family at all; they somehow manage as best they can; your Mom will do that, as well.

If your mom does not need your care and is living alone and coping with day to day life why do you need to check in on her daily?
Call once a week or once a month to check in.
IF there are cognitive problems you can encourage her to move into Independent L:iving and as she declines transition to Assisted then Memory Care. But you can not "force" her to move.
And when the time comes if she does need to be cared for you can petition the court that they appoint a Guardian if you do not wish to provide care directly or indirectly. (If she does not appoint you POA you would have to be appointed her Guardian anyway)

Perhaps you need to cut back to once a week.

Toxic people, even if it is your mother, do not need to be tolerated.

Your profile says your mother is (only) 79 years old and doesn't list any disabilities so I have to ask - why do you think you have to be in touch with her daily?