In an "at will" employment relationship, an employer has a great deal of discretion in setting the terms and conditions of the workplace. Accordingly, it can require holiday specific attire. That is unless a dress mandate of this type violates the company's own policy, a union agreement or employment contract. Also, no form of actionable discrimination must be a factor in your daughter's treatment.She should be aware that an at will employer can dismiss an employee for this reason, any reason or not reason at all, with or without notice. So she would be well advised to don the apparrel unless she wants to risk termination.Note: If she is discharged over her continued refusal, it would be for cause. Therefore making her ineligible for unemployment benefits.