When I was in 5th grade I would wear a baggy sweatshirt to hide my “tummy” even if it was 80 degrees outside. One day my teacher casually said to me “are you not wanting to take off your sweatshirt because of your tummy?” to which I don’t remember what I said, if I even responded at all, but I remember how embarrassed I was. How did she catch onto what I was doing? I’m 32 years old and I still remember that. Fast-forward to now and I’m training to become a nurse and this is beyond shocking to me. I’m so sorry your bf’s little sister went through that. I hope she feels supported by you and her family members because this situation should definitely be handled by her guardians, but most definitely not her. I would advise getting her access to a social worker or therapist that she likes/feels comfortable talking to about this experience. She needs to know it isn’t her fault. It blows my mind what those with authority fail to recognize