A girl has known her for over ten years. She has a boyfriend and knows that I have always liked her. She joked with me that she could dig corners. What do you mean?

That means: she also knows that you like her, and she likes you herself, but girls are thin-skinned, how dare they chase you back? I told you that you can dig the corner, which means that if you take the initiative to pierce the paper and profess to pursue her, she will be happy to be dug away by you. After all, it has been more than ten years. See if you really like her. If you like her, you should have the courage to express yourself.