In my opinion the woman was trying to make quick money, so she resorted to known methods of speeding up the brewing process. What she did not know is that she had put too many checmicals in the brew that would end up killing these people. She did not deliberately poison these people, but she contributed to their death by mixing too many chemicals into the brew, therefore making it toxic. She deserves 10yrs+, but not the death penalty.
http://www.the-star.co.ke/news/2016/10/10/woman-sentenced-to-death-for-killing-five-with-laced-brew_c1435425