My teacher recently put me in charge of being a mediator for my friend and her bully. I'm 13 and have a lot on my plate right now. My friend, we'll call M is 12, and we'll call the bully N, who is also 12. We were able to talk a little before both sides walked away before I could try to difuse the situation. I'll mention this, I am socially anxious, especially at school so this is not my specialty. So what happened is M is concerned about her dying dog and N brought up her dead dog so M told N that she didn't care about N's dead dog. I was with M a few minutes after and I said, "While N brought up her dog at the wrong time you shouldn't have said that because it made tension worse despite it being valid to feel that way." She turned on me and said, "Oh so I am the problem. Should I be the one moving schools?" I feel bad for M but at the same time I never wanted to be a mediator, I only wanted to be involved to defend M but I was only getting half the story and it seems M started it and even she said something that confirmed the incident which was some random game and something happened. So AITA?