Asking this one for a friend located in the United States. 

She's currently experiencing significant stress coming directly from her place of employment. All attempts to mediate this with her coworkers and boss have apparently failed and one of the benefits of her employment is a series of free optional visits to a psychiatrist hired by the company. She thinks this has the potential to help and might put her mind at ease until she can work out another place of employment.

I'm being told that, if she were to express herself openly and her grievances were to get back to management, she would almost surely be fired (and possible a couple other coworkers might get fired as well if she's taken seriously.)

Under normal circumstances I would cite standard doctor-patient confidentiality clauses that should at least guarantee nothing she says leaves the room and certainly doesn't get back to her boss. But I also know from experience, even from questions on this site, that confidentiality breaches happen all the time and don't tend to end well for the employee even if they're in the right.

Is it wise to trust psychiatrists employed by a business with business issues?

EDIT: I'm noticing there's some drift in the answers, so I'd like to clarify something: it's understood that it is illegal for the psychiatrist to lie about her confidentiality. That's known. What isn't known about this is how smart of a practical option this is. 

As a trivial example, there are tons of questions about [discovering fraud](https://workplace.stackexchange.com/questions/62686/my-employer-is-forcing-its-employees-to-defraud-its-customers-how-should-i-hand) that would be trivial to answer if you assume that the laws will protect the employee. Based on the answers, that doesn't always work out.