@BCS I can understand it taking a few days to process what just happened. It's such a shocking turn of events that you'd need some time to come to terms and I can understand that she could react in a variety of ways.
She definitely doesn't want to lose the family she has after she's fought for them, but when she realizes what her son has been doing, she knows that it will fracture apart like it did with her husband, and that probably scares her. The manga itself makes it out as if she's feeling a lot of conflicting emotions, and its understandable that if you husband was revealed to be a pedophile, and then your anti-social son with mental issues begins to assault your daughter, you probably would be in denial at first or so taken aback that you wouldn't know how to immediately act, especially because of the mental health aspect, their already poor relationship, and the fact she doesn't know how to respond to this situation. The entire thing is just confusing.