If you send a message to a girl and care about her, what does it mean that she doesn't reply?

If you send a message to a girl who cares about her and she doesn't reply to you, generally speaking, unless she didn't see it or didn't reply to your message in time because she was busy, then one possibility is that she doesn't like you, and she shows her attitude in this way, so that you can retreat. Another possibility is that this girl doesn't actually contradict you, but she still lacks a certain understanding of you, so she won't reply to your message for the time being.