Open Question: I am human resource assistant and my boss always tells me to do something out of my job description.?

I assist the in office work by training, setting-up meetings, calling, filing, mailing ad sometime interviewing. However, lately my boss has been hard on me. She tells me to clean outside the office such as the break-room and now she is even talking about checking the bathrooms. I was hired as human resource assistant and when I was taking the job I was not told what she is telling me to do now. So can my boss do this to me? What does the law says about this? To me this is this is demotion, but what do you think I should do to stop this before it gets out of hand? Any good advices. Thank you