What if the girl suddenly doesn't reply to the message?

First of all, we should know what the other person is thinking or doing at this time. There are usually three situations where no information is returned:

First of all, the other party is in a bad mood and doesn't want to reply.

Secondly, what you said offended the other party, and the other party expressed his anger with a cold attitude.

The third kind is simply busy, regardless of your last information, learn to judge each other's psychology, so as to properly handle the relationship.

If you keep talking normally, and the other person doesn't show emotion or is dissatisfied with what you say, it's probably because something else has affected your mood.

At this time, if you are chatting with the other person, don't express yourself at length, or say something irrelevant, so she will only be more annoyed.

If you notice that the other person is impatient, you can tell him directly. Look at you unhappy. Tell me what happened. If you don't want to talk, I'll take you for a walk.

If the other person still doesn't reply to you, don't bother the other person for the time being, and then reopen the topic when they deal with things or emotions.