Chatting with a girl I like, I sent her greetings on New Year's Day and didn't reply. I just asked her what she was doing. An hour has passed and she hasn't answered me yet.

She probably thought your greeting was a mass message, so she didn't reply.

I may not have time to call you back when I am at the theatre.

But maybe she is not interested in you, knows that you want to chase her, and doesn't want you to misunderstand that she is interested in you before chatting with you, so ...

That's what I did anyway ...