First, this is a bad example as you only get a ticket for running red lights (or jaywalking or driving over the speed limit). To your point, we all break the rules at one time or another. When we do this we are taking a risk of getting caught and dealing with the consequences. She knew the consequences and she took the risk.

That being said, I do empathize and if they had decided to be lenient, I personally see no reason to object. Furthermore, I don't think marijuana is a performance enhancing drug, and so I don't think there is a real point to the rule. If there is moral to the story, it's that we should get rid of the rule.