"long overdue?" So you're saying she should have D him long ago?
Relationships don't fall apart very often because "he" deserved it. There are two people with problems from many sources including how they were raised - which isn't in their control.
Maybe it is the right decision and maybe she should have given up sooner. Maybe. That is her place to judge and only her place. Blaming him and encouraging Luvless to blame him will not make things better.