Must we pay for time spent preparing to work?

Q. We have an employee who regularly comes into work a half-hour or more before her scheduled shift in order to get her work station ready and otherwise get herself set up for the day. This preparation time is important to the employee because she does not believe that she can meet the production requirements of her job without it. The employee has been told that she cannot start performing her actual job tasks until the start of her scheduled shift. Our new HR manager has advised that we must pay the employee for the time that she spends preparing for her shift, even though she had no approval to work during that time. Is that right?