What is the Sharʿī ruling on dealing with a female manager who practices magic and sorcery, and is it permissible to inform her husband of that?

There is no obligation to inform the man's wife. Rather, it is obligatory to strive to change the evil, such as convincing the manager to stay away from the foreign woman, and performing ruqyah on him if possible, and forbidding the woman from dealing in magic. If it is proven that she uses magic, then the competent authorities can be informed.