It's bad to give people the silent treatment.
Liz is trying to read her book on a bus but another passenger keeps trying to talk to her.
Liz wants the passenger to leave her alone.
Liz tells the passenger that she's just not in the mood to talk and wants to read her book.
Liz simply doesn't respond to anything the passenger says and stays quiet.
The passenger sees that Liz isn't feeling very social and leaves her alone.
The passenger feels that she is being treated very rudely by Liz and stops talking to her.