It is the company employing her, not the other way around. Company has policies and procedures. If I'm bound not to disclose the details of project I'm working at some company, does it violate my freedom of
speech?
Personally I think the courts should force companies to adopt a company headscarf as part of the uniform. Thats what they do in Britain, and everywhere else where immigrant comunities have been part of the fabric of society for a century.