Your student counselor is exactly that — a student of counseling. She has had classes and practice in doing counseling but she is just starting out. All counselors begin this way. The only way for us to get experience is to be a beginner at the actual art and science of therapy.
That doesn’t mean that your counselor can’t be helpful. She is supervised by an experienced therapist who regularly goes over her cases to offer advice and guidance. Further, since they are still in school, new therapists are often on the cutting edge of what is being learned about effective treatment. They bring a vitality and eagerness to help that in many ways makes up for their inexperience.
By all means, tell your counselor about the self-harm. Therapists, however long we’ve been doing therapy, rely on the client to give us the information we need to understand you and to help you. Since it’s hard for you to talk, why don’t you just bring your letter to the next session? If the counselor feels she can’t handle what you tell her, she’ll discuss it with you. It’s unlikely that you’ll be asked to switch therapists but if you are consider this: For you to heal, it’s more important to have a counselor who is confident about her skills for working with your issues.
I wish you well.