ual Discrimination?

I work for a large American car rental company at a local branch. Part of the job description for management trainee's, drivers, and everyone else is they may have to wash and vacuum a car when needed. Our office employs a young lady who worked at her job until her 8th month of pregnancy, and of course everyone at the office didn't ask her to wash cars because of her condition. She took a leave of absence for a few months to give birth to the child and recover. Now she is back and she refuses to wash and vacuum cars because she is a woman. Women at other branches wash and vacuum cars but our store manager says it's "not right" to ask a woman to wash a car (even if it is in her job description). Now everyone else in the office has to wash cars for her and her customers as needed; drop what your doing and quick, wash this car for me. One male coworker has quit over this issue and my job is harder now although the boss says i need to have a team player attitude. We also live in a "right to work" state...which basically means you can be fired for any reason at any time. I don't have an issue with the woman personally but i do have an issue with the boss who makes up the rules to fit his needs at the time. Is he breaking the law? How would i bring a ual discrimination suit against the company? I am apprehensive of retaliation, i need a job and i 'd hate to get fired. How would they settle? Thank you in advance.