My mother booked a ticket to visit me without my full permission, what should I do?

So basically my mother was supposed to visit me sometime and we planned not more than one week. She ended up getting sick and she postponed her ticked. She chose to stay a little over 3 weeks for this next stay without consulting this case with me and claimed that it was the cheapest ticket.
So the problem is I live in a small room in a shared flat and I also have to study and work. She fully knows that since I discussed it with her and told her that 3 weeks is just too long. My mother said she won't bother me and she could just go out alone ( but then I don't get the point about her visiting me? and she's still gonna sleep in my room so)
I got into a bad fight trying to convince her to stay for a shorter period but she didn't budge and honestly I don't know what to do.
My flatmates are also not too happy about this and I really understand their point of view. I want to try and convince her to take an earlier ticket home, which I can pay for but she's already coming in 2 days and I don't want to seem rude and worry her even more since she's also been having some health problems lately.

My mother booked a ticket to visit me without my full permission, what should I do?
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