Roommate has too many long-term guests
I have lived with my roommate since January. We are both on a month-to-month situation with our building, with no lease. My roommate has a lot of friends in different cities and this has led to frequent long-term house guests who stay with us when visiting the city. When I say long-term, I mean usually about two weeks. I have been mostly fine with it up until now, and I feel that allowing a two-week guest to stay is extremely generous on my part. However her most recent house guest, who is here right now, intends to stay for SIX weeks. I found this out at the last minute, after it was too late to stop it from happening, but I let my roommate know that I was not happy about the situation.
Then, on top of that, this particular houseguest is sleeping in the living room instead of my roommate's bedroom, which is additionally inconvenient because I can't use the living room or kitchen area late at night since she is sleeping. I have asked my roommate to have her sleep in her bedroom instead; my roommate flat out refused, which makes me so angry--after I have been INCREDIBLY patient with her numerous houseguests and she won't be even a little flexible to make sure I'm comfortable? If she's not willing to bend, I'm inclined to say no to all future houseguests.
My question is, how do I prevent her from having them? If I say no what's to stop her from disrespecting my wishes and bringing them over anyway? Any advice would be greatly appreciated.