We are talking about parental alienation (though the term is currently being replaced by others) where a child rejects a loving parent and aligns himself or herself with the unhealthy parent.
In a recent judgement in UK, the case crossed the welfare threshold, which meant that the concern for the child was such that it crossed from private to public law.
In her blog, Karen Woodall, leading psychotherapist, working in this field, writes: In my experience, many of the cases of children’s alignment and rejection are properly placed within public law because these are not about the contact relationship between a child and parents but about the need for child protection due to harm being caused by the parent to whom the child is aligned.
Unfortunately, most parents do not receive fairness or justice and are unable to protect their children. Loving parents are unfairly erased from their children's lives and as such, we need protections for targeted parents, in order to protect children.