I have a few thoughts in no particular order:

1) you can just call and tell her it didn't feel like the right fit for you.

2) I don't really understand why you want to find a therapist at the same centre just because your psychiatrist happens to be there. It seems like an unnecessarily limiting strategy.

3) the feel of the physical space matters a lot to me too. I am by no means a neat freak but I totally get what you mean about not wanting to see a T with a messy or smelly office. My son had a pschoeducational assessment recently and that psychologist's office was cluttered and ugly (my son said it smelled like feet and farts) and I found it very uninviting. My couples T's office is fairly cluttered though not messy or smelly and even that feels a bit oppressive.