Taken from  a website
   
The problem:

A girl is at the funeral of her mother. She meets a nice guy that she didn’t know who also was at the funeral and they hit it off. She was busy at the funeral and didn’t have time to ask him for his number before he left. She tried really hard to track him down, but no one knew who he was or how to contact him. A few days later her sister dies and the police suspect it to be a murder. Who killed her sister?

The Answer:
She killed her sister. She was hoping that if someone else in her family died, the man she met at her mother’s funeral would show up again.