Legally actionable discrimination in the work setting has to do with an employee receiving lesser treatment than their co-workers due to their race, religion, age (over 40), disability, national origin, etc. Absent that, there is no workplace right for all employees to be treated equally or even fairly. Accordingly, unless this action violates the terms of an exisiting employment contract or union agreement, it is perfectly permissable under the law. In other words, your employer can offer an extended insurance plan to only one of its employees.