How do you say no to a client due to their roommate?

I have a client that wants to hire me, and I told her I would think it over. She didn't inform me that she had a male roommate prior to the meet and greet, and during the meet and greet tried to brush past it in a fast manner. After thinking it over the past 24 hours I decided the risk wasn't worth the reward, but now I am not sure how to tell her no, and that I am taking on the other client.

I have no issues with the dog, or really the owner it is just the fact there will be an unknown male.