Answer:
To find the man whom she knows nothing about, she kills her sister in expectation of his presence in the funeral.
Explanation:
This is a type of riddle that comes under psychological study. Questions like these are formed to understand the physic and mental thoughts of a person. To find the man, she kills her sister believing he would come for her sister's funeral too. In fact, an alternative solution is hard to find. She has to either stalk him or go through her mother's friends and connections. Otherwise, something like killing her sister.
