"Psychological Test" joke

This is a genuine psychological test:
It is a story about a girl. While at the funeral of her own mother, she met this
guy whom she did not know. She thought this guy was amazing, so much her dream
guy she believed him to be just that, she fell in love with him there but never
asked for his number and then... A few days later the girl killed her own
sister.
Question: What is her motive in killing her sister?
Give this some thought for a while before you scroll down.
Answer: She was hoping that the guy would appear at the funeral again.
If you answered this correctly, you think like a psychopath.
This was a test by a famous American psychologist used to test if one has the
same mentality as a killer. Many arrested serial killers took part in this test
and answered it correctly. If you didn't answer correctly - good for you.
If your friends hit the jackpot, may I suggest that you keep your distance.