After confessing my love to a girl via text message, she ignored me. What happened?

I guess she is not mentally prepared, or you are too abrupt. Try to get in touch again, keep the same way as before, and apologize for the abruptness last time. After a period of time, when the time is right, express it again, be more subtle, or feel her gestures keenly, interact in real time, and gradually escalate, haha.