This scene in The Sixth Sense sets up the emotional climax at the end of the movie where Cole tells his mom about his deep dark secret that he can converse with ghosts.

Cole's mom has been trying to cope with her son's seeming lack of communication and odd behavior that manifests itself in seemingly socially unacceptable or bizarre ways. Frustrated with the apparent lack of progress and the fatigue of being a single parent and working two jobs is taking its toll on Cole's mom. In this scene, there is already tension between the two even before the conversation starts, so the viewer knows that Cole's mom is upset about something.

Things reach a boiling point over Grandma's bumblebee pendant which Cole's mom holds dear. Unbeknownst to Cole's mom, Grandma has been taking it from her jewelry box because she likes it so much. When asked point blank if Cole took the pendant from her jewelry case, Cole can only truthfully answer No which causes his mom to lose her temper.