What do girls mean when they say ducks don't need to be used?

The word "duck needn't" is a homophonic combination of English word "duck" and Chinese word "unnecessary", which means "no, it's totally unnecessary".

"Ducks don't have to" is a homophonic stalk, but it's actually a shorthand for "don't have to", which means you don't need to do anything.

This word is usually used to mean that something is completely unnecessary or overreacted. A girl may say "ducks don't have to be" because she thinks something is unnecessary or not worth doing.