So my close friend (F23) and her boyfriend (M24) have asked if they can stay the night at my place after our mutual best friends birthday. 
She only just asked me. 
The party is tomorrow at 3pm 
And she has had more than 2 months to ask if she could stay the night. 

For the past week Ive been so busy at work, doing alooot of hours (which she has been aware about) that I’ve been so exhausted when I finally get home. The party is my only day off I will have this week.
So the house is a mess.  I feel embarrassed about it. 

She said in the message that “it’s totally fine if you say no 💕”  but near the beginning of the message she said that she wasn’t able to that her and her partner might no be able to go. It feels like a big guilt trip. 
  (They live 45min away from the party destination) she can’t drive, but her boyfriend does. 
If she had at least asked a week prior I would probably  say yes to them. 

I don’t want to be that person that is the reason that someone can’t go
but 
on the other hand I don’t want to drop everything willy-nilly, she needs to understand that she can’t do this kind of thing, that people won’t say yes to her all the time? 

AITA if I say no? 