So I (16F) joined the school musical in September, just like a few other girls. One of those girls was Sophie (12). At first everything was normal, but then Sophie started telling me a bit more about her home life and it sounded really harsh, her mom was really ab*sive, mainly mentally. I'm not sure if this is 100% true though since this is just what Sophie told me. At a certain point it got warmer and Sophie started wearing short sleeves. At first I didn't notice anything but then sh cuts appeared. It started with a few, but it got worse with the day and I got really triggered since I'd struggled with sh in the past. Eventually we had the musical shows and she had to wear short sleeves in the show, and after seeing her arm like that for the whole day I just couldn't bear it anymore. So the next day on the second show I asked a member of the musical crew if they could make her wear long sleeves, which Sophie definitely didn't like because it was too hot. I understood that ofc but seeing the fresh sh really triggered me and 3 other girls. Anyway, the next day, the day of the third and last show, I bought her a sleeve to cover her arm. I told her I was sorry for making her wear long sleeves but that I was just really triggered and Sophie said she understood. She wore the sleeve and I thought this was a good compromise, but then I guess she got urges again and started to do sh again. But instead of taking the sleeve off to do it under there, she started doing it on her other arm and also her hand. I guess she did her hand because we couldn't make her cover up her hand. I just don't understand why she did this and why she wanted to ruin my fun day. Honestly now I think she does it for attention, maybe it's a cry for help but I already tried to help and support her so many times but she didn't want help with anything. She told me she did sh because she wanted her mom to see how badly she hurts her, but her mom wasn't around on the day of the third show, so why was it such a problem to just cover it up? I don't think it's just about her mom. Honestly I got really pissed and I don't understand why she did this. I talked about this with my mom and she said that sh isn't rational and she got the urge to do it and didn't think about where to do it. But I previously struggles with it, and it actually is quite rational. Before you sh you think about where to do it because you probably want certain people to see and others to not see. I just don't understand why Sophie wanted to ruin my day, but I can't help but wonder if I've done something wrong. AITA?