How should girls reply when they say good night?

Honey, it depends on your current relationship. If you are a boyfriend or girlfriend, you can reply: "Good night, don't miss me, otherwise I can't control your insomnia."

An ambiguous relationship can be answered: "Your bed is too small, move in and save a place for me."

Humorous words can reply: "Please go to sleep quickly and don't torture your mobile phone."