New Roommates

Above, I’ve included a video of Sheldon from the Big Bang Theory with his roommate agreement that he lives by every day. It seems like a ridiculous thing, but when my roommate and I found out that our other roommate was planning on living with us, we seriously though about making a roommate agreement because we knew that we were going to have some problems. Eventually, though, we decided not to make one and we would be fine. Unfortunately, we were right about having problems. In our agreement, we were going to include a section about not having people over, especially ones that the rest of us do not know. Now, we definitely wish we would have because there are strange people in our apartment almost every evening, and we do not feel comfortable with some of them being there, especially since even our roommate does not know most of them very well. We want to ask her to not bring so many strangers to our apartment, but we do not know how to ask without making her angry or getting defensive. Have you ever had an issue like this with a roommate? How did you handle it?