My best friend is madly in love with my teacher, but he is not that interested in her. She is really sad and I can't watch her suffer like that. Since he was my teacher, I can't talk to him for her (if I do, it'll be like insulting her) and I really feel helpless. What should I do to make her happy? Will a guy feel sad when a girl whom he has been dating with leaves him? He doesn't love the girl, but wanted to sleep her?