You want your daughter to be able to come to you in time of need and the coach is not necessarily someone who is trained to handle her issues not will be providing any sort of professional assistance to her. Try to speak to your daughter initially about what had been going on in her life and discuss how is she coping with all of that. Self harming behavior is not a healthy coping mechanism and it may be more helpful in the long run to speak to your daughter about what you know. The coach is there to coach not necessarily to provide emotional nor psychological support. Their communication can still be open and in the line of what student coach need to discuss as it relates to gymnastics and not beyond that.