If you look at it in the wider terms of psychology of toxic and abusive relationships, Lundy Bancroft's 'why does he do that' and Issendai's blog on toxic personalities and relationship dynamics, even the Chump Lady covers it well in her famous blog, this is a very, very well known characteristic behaviour often seen a perpetrator of abuse.
A reasonable person will spend years trying to negotiate, explain, discuss, lay out the evidence, because the belief is that if the other party just understood, then a reasonable works-for-all solution can be found. They lavish endless amounts of thought and mental energy on trying to better understand their very difficult relative/ex and what motivates them, without realising that all this effort is about:
-
the one causing all the crisis enjoying further being the constant centre of attention and headspace and focus and feeding off this
-
enjoying the delay of the unhappy party ever getting round to escaping or putting down barriers because another conversation or another strategy or another read book with ideas might yet help sort this out reasonably, and this spares the abusive party having to lose their victim or do anything uncomfortable like changing or coping without their supply (see cake. having cake, eating cake, all the cake.) If she looks like losing the will to continue, they often throw out another round of burble and wild ideas for her to waste a bit more time unpacking while they use her AND crack on with their own plans and need meeting.
-
there is no chance ever of having a reasonable conversation or outcome unless there are two parties with equal capacity for reasonability.
Freedom Programme. Strong boundaries. LC to NC. The relationships board have reams and reams on this.
Local authorities will also tell you about service users who tie up years of staff time and energy and money using their complaints system (often they have multiple running at the same time) as another means of endless attention and drama and engagement to no good purpose. Often multiple phonecalls and multiple huge emails a day, scattergun points, often hard to make sense of or not logical or connected, all of which demanding intensive answers. One service user with these behavioural challenges getting their needs met this way can cost several staff their careers in going off with stress or burn out. And the system has not yet developed the boundaries to identify an unreasonable person to be able to say no. No more. Not playing. Go and meet your needs through some other idiot.