I'm not going to hire a copywriter who confuses "kahunas" with "cojones."
Or who has missing punctuation, or poor formatting, or bad grammar, or incorrect use of idioms, or, or, or... Sure, "everyone's a critic" (and sorry to join the crowd), but if you're going to promote yourself as a professional copywriter you should at least have a grasp of the basics.
So I imagine she may well be able to help people who struggle with that. Which in my experience is almost everyone in business.