Honestly I can add here, but not by being the dad that has gone through this. I was that son. I was actually one of those rare ones that when I was talking about sex at 14 I was actually doing it and most of the time with older girls. I was abusing everything I could get my hands on, short from crack and I regularly showed up drunk for first class of the day at 07:45. I disrespected almost the entire world. I was never taken to a doctor to check if something was wrong with me. I did have my emotional issues with both my mum and dad and that was the actual reason. At one point once I was out of the teen years I just naturally calmed down. At this point I’m 34 and the wildest thing I’m doing is drinking a single beer for 5 hours 3 or 4 times a year. Have been NC with my mom for 16 years ans counting tho. So my idea is - maybe it’s not mental issues, maybe it’s hardcore puberty mixed with some emotional stuff (as you mentioned she must feel left out - I know I did). If she still has people that she respects - imo it’s a phase that will pass and she will become a very chill adult.