If a practitioner is using 9joules on you and thinks it’s effective settings, I would question the quality of her training, knowledge and her overall experience level.
She is totally mixing up concepts about ND:YAG and Alexandrite lasers. ND:YAG is most effective on thick/terminal hairs and Alexandrites are thought to be both effective on terminal and finer hairs. But if you have to sacrifice settings on Alexandrite because it will burn dark skin, there is no point using it. Low settings only make clinics rich and clients depressed.