Have you had a fortune told already at someone else's Katrina? In that case, you might not be able to have another one today.
Katrina will be open in my Main Street though and tells fortunes like normal. After your 20th, I think - but am not sure - that she will still ask to be built in your town when you are leaving.
edit: you can come to my town tomorrow if you'd like! After Googling, it seems like you can get 20 fortunes at other towns but she will only suggest the PWP at your town.
That's a shame thought I be able to get her the easy way by visiting other people towns XD.. And sure I would like to come on over tomorrow when I can x3..