I would think they are smelling the urine in the air. Their noses are so much more sensitive than ours. If she ever does start spraying I would not be allowing her to follow you into the washroom. JMO
Assumptions do nothing but make an ass out of u and me.
We can stick our heads in the sand for only so long before it starts choking us. Face it folks. The pet population is bad ALL OVER THE WORLD!