My elderly aunt and I live in the same city and I recently discovered that she offered up my apartment as lodging next month when my cousin (her daughter) comes to visit her (my aunt's apartment is very small). The problem is that not only did she not ask me beforehand, she didn't even tell me until now, a few weeks before the visit and it's a very inconvenient time for me to have guests.
I'm pretty miffed. Technically, I have the room but I don't really want to be a host for this cousin (I don't especially like her company) and I'm annoyed that it was forced upon me. But I also know all the plans have been made already and I don't want to rock the boat. What should I do?
I'm surprised that this cousin didn't contact you directly to check and see that this plan was okay before making her arrangements. That seems like the reasonable thing to do. So yes, I can see that this sudden intrusion is annoying.
You don't go into your cousin's circumstances or your relationship with your aunt but I'm going to assume a few things here. 1) You cousin can't (or won't) spring for a hotel or she probably would have just gone that route after your aunt said there wasn't room for her 2) Your elderly aunt might be getting a little forgetful and I'm sure didn't mean to leave you in the lurch.
Normally, I'd say you are under no obligation to host anyone you don't want to in your home, but in this case, you might just want to suck it up. It will be very nice for your aunt to have a visitor and this cousin will probably be spending a lot of time with your aunt during her visit anyway. I'd say either pay for her to stay in a inexpensive hotel or give her your guest room for a few nights and call it your good deed of the week.