I'm not familiar with the term "electro smog," so I emailed Annette Rugolo, who is a Master Dowser and teaches many of Marie's dowsing classes.
Here is her response:
"I’m not sure what this customer is referring to. It sounds like she
is connecting electro smog with underground water and feels there
would be some kind of confusion when trying to dowse for EMF’s when
it is energy actually created by aquafers?
I try to tell people that when you ask a clear question of your dowsing rods,
they will provide a clear answer. When asking for EMF’s, you are connecting
with the source of the EMF’s, wherever they might be coming from."
I hope this helps!