There are no black magicians, Muslim or otherwise. What there are, are some very strange people who like to get power over others; and some of these will call themselves magicians. If this girl is being harmed by an actual person, then that needs to be stopped; if something seems to be wrong with her, then she may need to see a doctor, psychiatrist or other professional. I do hope you manage to help her - but please don't delay getting help for her by looking for "magicians."