How do you deal with dancers who bring their friends in the dressing room? I don't like it. What can I do about it?
As with everything, it depends on many factors, but most of the time we want as few people backstage as possible. Politely let them know it's your workspace, not your playspace. Before the show it's awful to have people's friends backstage. Most backstage areas just aren't that spacious, and sometimes right before we go onstage we're mentally running our choreography in our heads and have trouble being sociable. Most experienced performers ask first, if they even consider bringing anyone back. If someone's making a documentary about you, I'm pretty sure I don't want them backstage at a moment's notice--ask about photography and videography backstage way in advance, not the day of the show. After the show it may or may not be okay, but it's usually more likely to be okay than before the show.
If someone doesn't believe me, check out this picture of a backstage scene at the Slipper Room and see if you see a whole lot of room for guests!