How can you have proof that someone didn't know something? There is no evidence that she did!
This depends on the complexity of the task. Knowing that pointing a gun at someone and pulling the trigger is ascertained though imitative learning. 99% of the worlds population learn about guns as kids watching shooting in films and TV.
On the other hand there is no evidence that Jeremy knew how to stage a suicide with all the typical trajectories, locations and bloodstains so even pathologists fall for it. This is a complex task that needs education. It cannot be achieved on common sense and native intelligence that developed simply by growing up.