This is a genuine psychological question . It is a story about a girl. Whilst at the funeral of her own mother, she met this guy whom she did not know. She thought this guy was perfect - so much her dream guy that she fell in love with him there and then. A few days later the girl killed her own sister. Question: What is her motive in killing her sister? < think about it for a while and I'll send the theory part around in a bit >