In a situation where a supervisor is attempting to make submission to sexual activity a condition of your employment, conduct can be illegal in two cases; First if there is a tangible employment action, such as a termination, denial of promotion, demotion, transfer, disciplinary action, or other significant change in your employment status, than the is highly likely to be illegal. If there was no tangible employment action, then her conduct must have been severe or pervasive for it to be against the law. If the request only happened once, then it is unlikely to be considered pervasive; depending on the circumstances, it may or may not be considered severe. You may wish to discuss what happened with a lawyer, coworker, supervisor, or human resources manager to determine whether you might have grounds for a lawsuit, or whether your company has a policy that would be violated by this behavior. Perhaps a solution can be reached that does not involve filing a formal complaint or lawsuit, such as a job transfer which would prevent you from working with this person on a daily basis.