On that day, the four of us went out to have breakfast together. Are you done? I joked with her best friend about paying the bill, so my girlfriend got angry with me? What do you think we should do?

This woman is indeed not worthy of you continuing. To be honest, saying that a best friend is always more important than a boyfriend is just fine if you think so in your heart, but it is extremely disgusting when you say it out loud. It does not mean to respect you at all, nor does it consider your feelings at all. What would you do with a girlfriend like this? Her so-called best friends can't play with her either, they have a glass heart. How tired you are, leave early and be relieved.