My friend asked me this question while morning walk, I was not able to answer. (am happy that i didn't, will tell you the reason later).
A woman was attending her mother's funeral. She meets a man she's never seen before. She believes him to be her soulmate and falls in love with him. But she forgets to ask for his number, and when the day is over, she can't track him down. A few days later she murders her sister.
p.s. : Try to answer it with the first thing which comes to your mind!
I've searched for the actual source, will be adding it after it is answered.