Considering all the serious teenage bullying problems nowadays... 1) Tell the girl that you will let parents know2) Tell parents ASAP your heard that the girl seems bullied and struggling3) Tell the girl to go to talk to her school counselors ASAP4) Tell the girl that you are not a counselor but a piano teacher, so you can't really help her on those issues. You hope mastering piano will help her feel better about the situation, and you can only help her achieve such.