My girlfriend asked me to choose between her and my good brother. What should I say?

This question is both difficult and simple. Choosing her means choosing a friend instead of a brother. I can't bear to part with my brother when I choose her. She also said that you were not responsible for her, and called you heartbroken! Obviously, she wants you to make this choice, because she is a girl who is not sensible. In my opinion, I chose her to let your brother know that she must make this choice, and you love her very much, hoping to get your brother's understanding. Generally speaking, as a brother, you can understand and respect your choice, so as not to hurt each other, which is also the so-called best of both worlds, don't you think?