If you have a side chick without getting caught that means your girlfriend is also cheating because faithful girls are very good at monitoring every movement of their boyfriend. They can go to any extent to investigate and ascertain whether their boyfriend is having another relationship or not. Girls and ladies in the house is this very statement true.

They are the intelligent department, they won't make the investigation look obvious.

It is more likely that a girl that is cheating will do more snooping around. A man or woman that is cheating is more suspicious of their partner. She'll catch you cos she knows all the tricks.