The Grey Rock method sounds excellent. I would love to pass this on to a friend of a dd, whose mother certainly strikes me as toxic - constantly belittling her, calling her thick, ruining her relationships by being scathing about every nice bloke she ever had, not to mention being horribly rude to them in person. In the past she’s been vile to my own dds, too.
Now long grown up, the dd can’t seem to keep away, or even cut down contact - it’s as if there are invisible cords, endlessly pulling her back.
And I don’t know why someone always has to suggest that such a person is ‘unwell’. Some people just are unpleasant or downright nasty.
As for Allsorts saying that we have a responsibility to our parents, no matter how unpleasant they may be, I would say it surely comes down to ‘Do as you would be done by.’ Or, as my DM was fond of saying, ‘You reap what you sow.’
But I might add that although I have a very good relationship with dds, there is no way I ever want or expect them to look after me in old age. I have told them as much very firmly, and have also made a point of it in my Health and Welfare Power of Attorney.