My DH had a very difficult relationship with his mother, boarding school at the early age of 7, divorced, then absent father, (abroad with new lady), neurotic mother, necessitating school holidays with grandmother, etc! Horrible to me over many years, making contact with her very difficult, but even so for all this, as she got older and eventually frail we,and DH's two siblings did make sure that she was looked after appropriately and visited, not that often I'll admit, but enough; Carers, and latterly the Home contacted on a regular basis and her well being kept an eye on. She was his mother and to leave your own mother to fend for herself in old age, however awful she's been, imo says more about you than her.