Finding the object with which you suspect your daughter is self-harming is an opportunity to address the issue with her and communicate your concern as a parent, from a calm attitude, without making her feel judged, and offering her help.
In general, it's advisable to make a commitment to the student that their self-harm problem will not be disclosed to anyone, but it's also essential to have the support of the rest of the crisis team, the parents, and perhaps the intervention of a