I didn't reply to my girlfriend's message. How could I be angry?

Explain the reasons, show concern, sincerely apologize, etc.

1. Explain the reason: I didn't reply to the message in time because of some special reasons, such as busy work or other urgent matters. You can explain to her. Let her know about you, so that she will understand you better.

2. Show concern: You can ask your girlfriend how she is recently and if there is anything she can do to help. You can express your concern and love to her and let her feel your warmth.

3. Sincere apology: apologize to your girlfriend, admit your mistake and express your apologies to her. You can tell her that you didn't reply to the message in time because you were busy or for other reasons, not because you didn't care about her and didn't pay attention to her.