Can an employer force an employee to take an unpaid lunch break?
My mother works 6 hours a day and never took breaks before. Now out of the blue her boss wants her to take a 30 minute unpaid lunch. He will not state why. The boss does not make a 7 hour per day younger male co-worker take a break. The lost time cannot be made up. My mother has been working in a similar capacity for over 40 years in food service without taking a lunch. There is plenty of work that won't get done if the employees take lunch.
Unfortunately, your mother's boss probably can make her do this. Employers have near-total discretion to set hours, so just as the employer could shorten her day by 1/2 hour by starting later or ending earlier, it can have a non-working break in the middle. (If she actually does any work during that time, or is not free to leave the premises on her break, then it may count as work time, however.)
You mention a younger male coworker who is treated differently. If your mother believes that the differential treatment is due to either her sex/gender or her age (over 40; assuming he is under 40), then she *might* have an employment discrimination case, and may wish to consult with an employment law attorney to explore the possibility in greater detail.
Assuming the motive for requiring the lunch break is not discriminatory as prohibited by state and federal laws against discrimination, there is no legal prohibition against requiring an unpaid lunch break as you described.