There are a couple of things that could be done, but I cannot guarantee the results you want. Your husband and fellow employees could file a grievance with the company. It sounds like the company has a lawyer-written personal policy and a grievance procedure should be part of the manual.
Secondly, they can complain to the U.S. Department of Labor, on several grounds, including the person not being qualified, sexual discrimination and possible OSHA violations, since the person is doing a job for which she is not qualify, she could cause injuries to personal or damage to the facility.
Depending on the size of the company, if anyone has a rapport with a higher up supervisor, make sure he or she is aware of the issue.
If the plan is unionized, definitely contact the union personnel.
I was faced with a similar situation once. We had a secretary. Our vice president thought she could do no wrong. She got a promotion, she had some of her duties assigned to the other secretary and they were close to splitting the office in half. I was looking for another job. The woman finally quit and things returned to "normal." Never was sure what normal was at that place.
Finally, your husband can hire his own lawyer. There should be no cost, if your husband is suing for lost wages--the lawyer's fee would come out of the settlement. If he loses there is no fee. Your husband probably would not lose his job, but he would probably never be promoted. Companies do not like lawsuits.
Unfortunately none of the options I have spelled out for you are great. I would first try talking to someone in upper management, if that is possible--try to determine if the offending party has any "connections" with management. If that option is not available or does not accomplish anything. I would contact the U.S. Dept. of Labor. The wage and hour people do unannounced audits all the time and if they have a clue of something being wrong, they might be able to get it corrected.