If you really want a therapist, go out and contact some. Find the one that's best for you and then start to come up with a dialogue of what you are going to tell your parents. This way they know you are serious about your problem and you desperately want help. And tell your friend this too, if she wants you to tell your parents, tell her to help you with getting yourself prepared. Also, if you would feel more comfortable with her around, ask her to be there with you when you tell them. She doesn't have the right to tell them honestly.