[MargaretR]

From the way that Mick described her behaviour (as a witness to it), I think she may well be displaying the personality changes which accompany Altzheimers disease.
Being argumentative and delusions of persecution, are both early signs.
I saw these changes in my father in his mid 60s. He did not die until his 80s,and of other causes, but by that time his Altzheimers was fully developed and he did not know who I was.
I still think that a fine was in order, but her behaviour then and since may alert her family to consider her mental health.