A woman is attending her mothers funeral when she meets a man their, she instantly falls in love at first sight, she never gets his name and never saw where he went after the funeral. A week later she kills her sister. Why did she kill her sister?

let me know if you want the answer or if you think you know the answer let me know and i will tell you if you are a potential serial killer. this same question was asked to several convicted serial killers by state psychologists and they all answered the same. just to let you know i did not know the answer until some one told me i guessed wrong the first time so no worries lol.