Sometimes the father now makes and takes a special time totally devoted to being with his children.
Often far more then he even managed to put together with them while married.
If he goes out of his way and makes special arrangements and asks to spend more or special times, with his children, she will often say, no, you can not do that, it would just be too disruptive, they are just getting settled after the divorce.
Seeing his children again for a short time is a reunion, followed shortly by an emotional painful parting.
However, because of what he is doing to her by leaving, she will feel she is justified and the kid lever gives her power and gets his attention.