A therapist isn’t going to judge her but a competent one would ask her whether she thinks that is fair, to ask him to choose between his kids from his previous marriage and her. They would also likely work on them finding better ways to meet each other’s needs. Counseling with a WAS is usually a waste because they aren’t genuinely interested in fixing things when they’ve got an AP in their sights. But a situation like this is different - and even if the relationship isn’t salvageable, it might help improve their co-parenting communication going forward.