How does Mumbi explain to Mugo about her affair with Karanja?

Mumbi tells Mugo that during the Emergency the village was burned. Food and resources were scarce, and when Karanja got his government job, he started bringing her food, but she ignored him. This continued until Karanja told Mumbi that Gikonyo would be released from the camp. For some reason, she weakens to him, and they make love. Mumbi says she threw her shoe at him after.