Alienating parents typically also engage in another quintessential borderline pattern, a habit that therapists refer to as splitting. They enlist others to join their side in fighting against the supposedly evil other, splitting the family into us against them.
Individuals with borderline personality features get mad when someone of import to them won’t give them what they want—e.g., a spouse who has decided to leave the marriage, generally because the alienating partner was not capable of healthy, loving and collaborative partnership. Their goal then becomes to destroy the other parent’s relationship with the children. They corral in the children to join them in this battle as a fighter for their side. They do all they can to deprive the other parent, their enemy, of being able to continue to be a parent.