Barring people from my office

I really wonder if there's a way to keep people out of my office. One staff member comes in whenever she works and kvetches. Today she came in five times to complain about five different things. (We shouldn't keep so many new books when they're past a certain date...we shouldn't recover rentals..why don't we have DN on the labels it made it easier to shelf read.) I forget the rest She doesn't like my answers. (Recover them this time, I'll look into before the next round, which is four months away/I've gotten to many complaints about the lack of quantitiy none about the age of books/HQ sets the label standards, if they don't want it, we don't get it.) I am SO tired of being nagged at everytime she's in!! The worst part is that my office doesn't have a door.