Good Riddles

Question: A young woman is attending her mother's funeral. While there, she meets a man she has never seen before and falls in love immediately. After the funeral she tries to find him but cannot. Several days later she kills her sister.

Why does she kill her sister?

Question: When you do not know what I am, then I am something. But when you know what I am, then I am nothing. What am I?

Question: I'm teary-eyed but never cry.
Silver-tongued, but never lie.
Double-winged, but never fly.
Air-cooled, but never dry.

What am I?

Question: Smell me, buy me, and deliver me.
I won't change.

What am I?

Question: Without fingers, I point,
without arms, I strike,
without feet, I run.

What am I?