In the novel Purple Hibiscus, Mama kills Papa by putting poison in the tea that he shared with his children, which is not lost on Kambilli.
“Why did you put it in his tea?” I asked Mama, rising. My voice was loud. I was almost screaming. “Why in his tea?”
It seems like a pretty important thing to just leave out, as there is no direct answer that I can see in the text. Why did she choose his tea to poison him? Why would she needlessly want to risk the life of her children?