@tamerlane
I think regardless of the circumstances, this is Kanako's job. The client in this chapter was the woman who was implied to be hit. Sometimes it's not clear, but throughout this manga, all the people Kanako's killed are job assignments. It's why she's in the area in the first place and often has her phone out before she kills. The only instance I recall where she killed someone who wasn't on her list was that molester on the train, but even then, Sakurai said that someone probably ordered a hit on him already, and they just hadn't gotten to his name yet. Also, Kanako likes killing people, but she also knows it's wrong to enjoy that sort of thing, so she's always constantly trying to find ways to justify her actions. That's why we always see each target doing something awful before she kills, rather than showcasing positive characteristics that may give Kanako doubts. We aren't meant to put too much thought into whether these killings are just (if killing can even
be justified) , because Kanako certainly isn't.
Also, I feel that with the woman who ordered the hit crying, "I'm sorry, I'm just remembering everything up til now..." it's implied that the abuse was not an anomalous one-time thing or an accident/misunderstanding. (not that abuse is only valid after the second time one gets beat up or verbally/emotionally ripped apart, but I know many partners/family members endure it long after the first occurrence)