Travelinglady is right. Other infections can cause confusion which, at your mother's age, can be misdiagnosed as dementia. Chest infections are another cause.
Please seek professional help because you need to take care of yourself.
As I've mentioned before, your mother sounds like mine. There's no underlying factor for her attitude to me, she's just horrible and always has been. As my aunt (her sister) commented to me recently "Now I realise it's not all you". That was after a long discussion on recent events.